/*
 * This program is free software; you can redistribute it and/or modify
 * it under the terms of the GNU General Public License as published by
 * the Free Software Foundation; either version 2 of the License, or
 * (at your option) any later version.
 *
 * This program is distributed in the hope that it will be useful,
 * but WITHOUT ANY WARRANTY; without even the implied warranty of
 * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
 * GNU General Public License for more details.
 *
 * You should have received a copy of the GNU General Public License
 * along with this program; if not, write to the Free Software
 * Foundation, Inc., 675 Mass Ave, Cambridge, MA 02139, USA.
 *
 * TMS9928A.c
 *
 * Based on   tms emulation (C) Marat Fayzullin 1994-2021
 *
 */

//---------------------------------------------------------------------------
#include <string.h>       // C-standaard header voor o.a. memset (vervangt mem.h)

#include "tms9928a.h"
#include "video_bridge.h"
#include "coleco.h"
#include "z80.h"

// Externen uit de core
extern unsigned char cv_display[];   // schermbuffer met palette-indexen
extern int cv_pal32[16*4];           // 0x00RRGGBB, 16 kleuren * 4 varianten

// Scherm breedte & hoogte (Globale Variabele DEFINITIES)
WORD TVW, TVH;

void _TMS9928A_mode0(unsigned char uY);
void _TMS9928A_mode1(unsigned char uY);
void _TMS9928A_mode2(unsigned char uY);
void _TMS9928A_mode3(unsigned char uY);

// Screen handlers and masks for tms.VR table address registers
const tScrMode SCR[MAXSCREEN+1] = {
    { _TMS9928A_mode0,0x7F,0x00,0x3F,0x00,0x3F, 0x00,0x00,0x00,0x00 },   // SCREEN 0:TEXT 40x24
    { _TMS9928A_mode1,0x7F,0xFF,0x3F,0xFF,0x3F, 0x00,0x00,0x00,0x00 },   // SCREEN 1:TEXT 32x24
    { _TMS9928A_mode2,0x7F,0x80,0x3C,0xFF,0x3F, 0x00,0x7F,0x03,0x00 },   // SCREEN 2:BLOCK 256x192
    { _TMS9928A_mode3,0x7F,0x00,0x3F,0xFF,0x3F, 0x00,0x00,0x00,0x00 }    // SCREEN 3:GFX 64x48x16
};

tTMS9981A tms;

// ----------------------------------------------------------------------------------------
// Qt video-bridge helpers

static inline void _push_cv_scanline(int y_core)
{
    // y_core = 0..191 (al gecorrigeerd met TMS9918_START_LINE)
    static uint32_t line[VB_WIDTH];

    // In EmulTwo staan de 256 pixels horizontaal gecentreerd in TVW, idem verticaal in TVH
    unsigned char *row =
        cv_display
      + TVW * (y_core + (TVH - 192) / 2)
      + (TVW / 2 - 128);

    for (int x = 0; x < VB_WIDTH; ++x) {
        int idx    = row[x] & 0x3F;        // palette index (defensief)
        uint32_t rgb  = (uint32_t)cv_pal32[idx];
        line[x] = 0xFF000000u | (rgb & 0x00FFFFFFu);
    }
    vb_present_scanline(y_core, line);
}

// ----------------------------------------------------------------------------------------
// Reset the tms.VR
void tms9918_reset(void) {
    unsigned char i;

    memset(tms.VR,0x00,sizeof(tms.VR));                          // Init registers
    memset(VDP_Memory,0x00,0x4000);                              // Init VRAM

    tms.VKey    = 1;                                             // address latch key
    tms.SR      = 0x00;                                          // status register
    tms.FGColor = tms.BGColor = 0;                               // voor/achtergrond
    tms.Mode    = 0;                                             // huidige screenmode
    tms.CurLine = 0;                                             // huidige scanline
    tms.DLatch  = 0;                                             // data latch
    tms.ScanLines = TMS9918_LINES;                               // NTSC default

    tms.MaxSprites = TMS9918_MAXSPRITES;                         // chipset default
    tms.ChrTab = tms.ColTab = tms.ChrGen = VDP_Memory;           // tables (screen)
    tms.SprTab = tms.SprGen = VDP_Memory;                        // tables (sprites)

    tms.ColTabM = ~0;
    tms.ChrGenM = ~0;

    tms.UCount  = 0;
    tms.VAddr   = 0x0000;
    for (i=0;i<16;i++) tms.IdxPal[i] = i;

    tms.VR[1] |= TMS9918_REG1_SCREEN;  // scherm aan bij boot
    tms.BGColor = 0;                   // zwart als achtergrond (coleco-pal index 0)
    tms.FGColor = 15;                  // wit als voorgrond

    // Init screen size
    TVW = TVW_TMS;
    TVH = TVH_TMS;
}

// ----------------------------------------------------------------------------------------
unsigned char Write9918(int iReg, unsigned char value)
{
    unsigned char J;
    unsigned int VRAMMask;
    unsigned char bIRQ;
    unsigned char old = tms.VR[1];   // <-- NIEUW (oude Reg1 bijhouden)

    // IRQEN 0->1 terwijl VBlank al 1 is?
    bIRQ = (iReg==1)
        && ((old ^ value) & value & TMS9918_REG1_IRQ)
        && (tms.SR & TMS9918_STAT_VBLANK);

    // VRAM 4k/16k mask update check
    VRAMMask = (iReg==1) && ((old ^ value) & TMS9918_REG1_RAM16K) ? 0 : TMS9918_VRAMMask;

    // Register schrijven
    tms.VR[iReg] = value;

    switch (iReg) {
        case 0:
        case 1:
            switch (TMS9918_Mode) {
                case 0x00: J=1; break;
                case 0x01: J=2; break;
                case 0x02: J=3; break;
                case 0x04: J=0; break;
                default:   J=tms.Mode; break;
            }
            if ((J!=tms.Mode) || !VRAMMask) {
                VRAMMask    = TMS9918_VRAMMask;
                tms.ChrTab  = VDP_Memory+(((int)(tms.VR[2]&SCR[J].R2)<<10)&VRAMMask);
                tms.ColTab  = VDP_Memory+(((int)(tms.VR[3]&SCR[J].R3)<<6)&VRAMMask);
                tms.ChrGen  = VDP_Memory+(((int)(tms.VR[4]&SCR[J].R4)<<11)&VRAMMask);
                tms.SprTab  = VDP_Memory+(((int)(tms.VR[5]&SCR[J].R5)<<7)&VRAMMask);
                tms.SprGen  = VDP_Memory+(((int)(tms.VR[6]&SCR[J].R6)<<11)&VRAMMask);
                tms.ColTabM = ((int)(tms.VR[3]|~SCR[J].M3)<<6)|0x1C03F;
                tms.ChrGenM = ((int)(tms.VR[4]|~SCR[J].M4)<<11)|0x007FF;
                tms.Mode    = J;
            }
            break;

        case 2:  tms.ChrTab = VDP_Memory+(((int)(value&SCR[tms.Mode].R2)<<10)&VRAMMask); break;
        case 3:  tms.ColTab = VDP_Memory+(((int)(value&SCR[tms.Mode].R3)<<6)&VRAMMask);
                 tms.ColTabM = ((int)(value|~SCR[tms.Mode].M3)<<6)|0x1C03F; break;
        case 4:  tms.ChrGen = VDP_Memory+(((int)(value&SCR[tms.Mode].R4)<<11)&VRAMMask);
                 tms.ChrGenM = ((int)(value|~SCR[tms.Mode].M4)<<11)|0x007FF; break;
        case 5:  tms.SprTab = VDP_Memory+(((int)(value&SCR[tms.Mode].R5)<<7)&VRAMMask); break;
        case 6:  tms.SprGen = VDP_Memory+(((int)(value&SCR[tms.Mode].R6)<<11)&VRAMMask); break;
        case 7:  tms.FGColor = tms.IdxPal[value>>4];
                 value &= 0x0F;
                 tms.IdxPal[0] = tms.IdxPal[value ? value : 1];
                 tms.BGColor   = tms.IdxPal[value];
                 break;
    }

    return bIRQ; // compat
}

// ----------------------------------------------------------------------------------------
// Write a value to the tms.VR Data Port.
void tms9918_writedata(unsigned char value) {
    tms.DLatch = value;
    VDP_Memory[tms.VAddr] = value;
    tms.VAddr = (tms.VAddr+1)&0x3FFF;
}

// ----------------------------------------------------------------------------------------
// Read a value from the tms.VR Data Port
unsigned char tms9918_readdata(void) {
    unsigned char retval;

    retval = tms.DLatch;
    tms.DLatch = VDP_Memory[tms.VAddr];
    tms.VAddr = (tms.VAddr+1)&0x3FFF;

    return(retval);
}

// ----------------------------------------------------------------------------------------
// Write a value to the tms.VR Control Port. Enabling IRQs or not
unsigned char tms9918_writectrl(unsigned char value) {
    if (tms.VKey)
    {
        tms.VKey=0;
        tms.VAddr=((tms.VAddr&0xFF00)|value)&0x3FFF;
    }
    else
    {
        tms.VKey=1;
        tms.VAddr = ((tms.VAddr&0x00FF)|((int)value<<8))&0x3FFF;
        switch(value&0xC0)
        {
        case 0x00:
            // READ mode: prime DLatch and post-increment
            tms.DLatch = VDP_Memory[tms.VAddr];
            tms.VAddr  = (tms.VAddr+1)&0x3FFF;
            break;
        case 0x80:
            // Writing a register may generate IRQ
            return Write9918(value&0x0F, tms.VAddr&0x00FF);
        }
    }

    // No interrupts
    return 0;
}

// ----------------------------------------------------------------------------------------
// Read a value from the tms.VR Control Port
unsigned char tms9918_readctrl(void) {
    unsigned char retval;

    //retval = tms.SR | 0x80;  // forceer bit7 (test)

    retval = tms.SR;
    tms.SR &= TMS9918_STAT_5THNUM|TMS9918_STAT_5THSPR;


    return(retval);
}
// ----------------------------------------------------------------------------------------
// Compute bitmask of sprites shown in a given scanline.
// Returns the first sprite to show or -1 if none shown.
// Also updates 5th sprite fields in the status register.
int ScanSprites(unsigned char Y,unsigned int *Mask)
{
    const unsigned char SprHeights[4] = { 8,16,16,32 };
    unsigned char OH,IH,*AT;
    int L,K,C1,C2;
    unsigned int M;

    // No 5th sprite yet
    tms.SR &= ~(TMS9918_STAT_5THNUM|TMS9918_STAT_5THSPR);

    // Must have MODE1+ and screen enabled
    if (!tms.Mode || !TMS9918_ScreenON)
    {
        if(Mask) *Mask=0;
        return(-1);
    }

    OH = SprHeights[tms.VR[1]&0x03];
    IH = SprHeights[tms.VR[1]&0x02];
    AT = tms.SprTab;
    C1 = tms.MaxSprites+1;
    C2 = 5;
    M  = 0;

    for (L=0;L<32;++L,AT+=4)
    {
        K=AT[0];             // K = sprite Y coordinate
        if (K==208) break;    // Iteration terminates if Y=208
        if (K>256-IH) K-=256; // Y coordinate may be negative

        // Mark all valid sprites with 1s, break at MaxSprites
        if((Y>K)&&(Y<=K+OH))
        {
            // If we exceed four sprites per line, set 5th sprite flag
            if(!--C2) tms.SR|=TMS9918_STAT_5THSPR|L;

            // If we exceed maximum number of sprites per line, stop here
            if (!--C1) break;

            // Mark sprite as ready to draw
            M|=(1<<L);
        }
    }

    // Set last checked sprite number (5th sprite, or Y=208, or sprite #31)
    if(C2>0) tms.SR |= L<32? L:31;

    // Return first shown sprite and bit mask of shown sprites
    if (Mask) *Mask=M;
    return(L-1);
}

// ----------------------------------------------------------------------------------------
// Check for the sprite collisions and 5th sprite, and set appropriate
// bits in the tms.VR status register.
unsigned char CheckSprites(void) {
    unsigned int I,J,LS,LD;
    unsigned char *S,*D,*PS,*PD,*T;
    int DH,DV;

    // Find valid, displayed sprites
    DV = TMS9918_Sprites16 ? -16:-8;
    for  (I=J=0,S=tms.SprTab;(I<32)&&(S[0]!=208);++I,S+=4)
    {
        if (((S[0]<191)||(S[0]>255+DV))&&((int)S[1]-(S[3]&0x80? 32:0)>DV))
            J|=1<<I;
    }

    if(TMS9918_Sprites16)
    {
        for(S=tms.SprTab;J;J>>=1,S+=4)
        {
            if(J&1)
            {
                for(I=J>>1,D=S+4;I;I>>=1,D+=4)
                {
                    if(I&1)
                    {
                        DV=(int) S[0]-(int) D[0];
                        if ((DV<16)&&(DV>-16))
                        {
                            DH=(int)S[1]-(int)D[1]-(S[3]&0x80? 32:0)+(D[3]&0x80? 32:0);
                            if ((DH<16)&&(DH>-16))
                            {
                                PS=tms.SprGen+((int)(S[2]&0xFC)<<3);
                                PD=tms.SprGen+((int)(D[2]&0xFC)<<3);
                                if (DV>0) PD+=DV; else { DV=-DV;PS+=DV; }
                                if (DH<0) { DH=-DH;T=PS;PS=PD;PD=T; }
                                while(DV<16)
                                {
                                    LS=((unsigned int)PS[0]<<8)+PS[16];
                                    LD=((unsigned int)PD[0]<<8)+PD[16];
                                    if (LD&(LS>>DH)) break;
                                    else { ++DV;++PS;++PD; }
                                }
                                if(DV<16) return(1);
                            }
                        }
                    }
                }
            }
        }
    }
    else
    {
        for(S=tms.SprTab;J;J>>=1,S+=4)
        {
            if(J&1)
            {
                for(I=J>>1,D=S+4;I;I>>=1,D+=4)
                {
                    if(I&1)
                    {
                        DV=(int)S[0]-(int)D[0];
                        if ((DV<8)&&(DV>-8))
                        {
                            DH=(int)S[1]-(int)D[1]-(S[3]&0x80? 32:0)+(D[3]&0x80? 32:0);
                            if ((DH<8)&&(DH>-8))
                            {
                                PS=tms.SprGen+((int)S[2]<<3);
                                PD=tms.SprGen+((int)D[2]<<3);
                                if (DV>0) PD+=DV; else { DV=-DV;PS+=DV; }
                                if (DH<0) { DH=-DH;T=PS;PS=PD;PD=T; }
                                while((DV<8)&&!(*PD&(*PS>>DH))) { ++DV;++PS;++PD; }
                                if(DV<8) return(1);
                            }
                        }
                    }
                }
            }
        }
    }

    return(0);
}

// ----------------------------------------------------------------------------------------
// RefreshBorder: called from RefreshLine#() to refresh the screen border.
void RefreshBorder(unsigned char Y)
{
    unsigned char *P,BC;
    int J,N;

    // Border color
    BC=tms.BGColor;

    // Screen buffer
    P=cv_display;
    J=TVW*(Y+(TVH-192)/2);

    // For the first line, refresh top border
    if (Y) P+=J;
    else for (;J;J--) *P++=BC;

    // Calculate number of pixels
    N=(TVW-(tms.Mode ? 256:240))/2;

    // Refresh left border
    for (J=N;J;J--) *P++=BC;

    // Refresh right border
    P+=TVW-(N<<1);
    for (J=N;J;J--) *P++=BC;

    // For the last line, refresh bottom border
    if (Y==191)
        for (J=TVW*(TVH-192)/2;J;J--) *P++=BC;
}

// ----------------------------------------------------------------------------------------
// RefreshSprites: called from RefreshLine#() to refresh sprites.
void RefreshSprites(unsigned char Y)
{
    const unsigned char SprHeights[4] = { 8,16,16,32 };
    unsigned char OH,IH,*PT,*AT;
    unsigned char *P,*T,sColor;
    signed int L,K,N;
    unsigned int M;

    // Find sprites to show, update 5th sprite status
    N = ScanSprites(Y,&M);
    if ((N<0) || !M) return;

    T  = cv_display + TVW*(Y+(TVH-192)/2) + TVW/2-128;
    OH = SprHeights[tms.VR[1]&0x03];
    IH = SprHeights[tms.VR[1]&0x02];
    AT = tms.SprTab+(N<<2);

    // For each possibly shown sprite...
    for( ; N>=0 ; --N, AT-=4)
    {
        if(M&(1<<N))
        {
            sColor=AT[3];                   // C = sprite attributes
            L=sColor&0x80? AT[1]-32:AT[1];  // Sprite may be shifted left by 32
            sColor&=0x0F;                   // C = sprite color

            if((L<256)&&(L>-OH)&&sColor)
            {
                K=AT[0];                     // Y
                if (K>256-IH) K-=256;        // negative Y wrap

                sColor = tms.IdxPal[sColor];
                P  = T+L;
                K  = Y-K-1;
                PT = tms.SprGen
                    + ((int)(IH>8? (AT[2]&0xFC):AT[2])<<3)
                    + (OH>IH? (K>>1):K);

                // Mask 1: clip left sprite boundary
                K=L>=0? 0xFFFF:(0x10000>>(OH>IH? (-L>>1):-L))-1;

                // Mask 2: clip right sprite boundary
                L+=OH-257;
                if(L>=0)
                {
                    L=(IH>8? 0x0002:0x0200)<<(OH>IH? (L>>1):L);
                    K&=~(L-1);
                }

                // Get and clip the sprite data
                K&=((unsigned int)PT[0]<<8)|(IH>8? PT[16]:0x00);

                if(OH>IH)
                {
                    if(K&0xFF00)
                    {
                        if (K&0x8000) { P[0] = sColor; P[1] = sColor; }
                        if (K&0x4000) { P[2] = sColor; P[3] = sColor; }
                        if (K&0x2000) { P[4] = sColor; P[5] = sColor; }
                        if (K&0x1000) { P[6] = sColor; P[7] = sColor; }
                        if (K&0x0800) { P[8] = sColor; P[9] = sColor; }
                        if (K&0x0400) { P[10] = sColor; P[11] = sColor; }
                        if (K&0x0200) { P[12] = sColor; P[13] = sColor; }
                        if (K&0x0100) { P[14] = sColor; P[15] = sColor; }
                    }
                    if(K&0x00FF)
                    {
                        if (K&0x0080) { P[16] = sColor; P[17] = sColor; }
                        if (K&0x0040) { P[18] = sColor; P[19] = sColor; }
                        if (K&0x0020) { P[20] = sColor; P[21] = sColor; }
                        if (K&0x0010) { P[22] = sColor; P[23] = sColor; }
                        if (K&0x0008) { P[24] = sColor; P[25] = sColor; }
                        if (K&0x0004) { P[26] = sColor; P[27] = sColor; }
                        if (K&0x0002) { P[28] = sColor; P[29] = sColor; }
                        if (K&0x0001) { P[30] = sColor; P[31] = sColor; }
                    }
                }
                else
                {
                    if(K&0xFF00)
                    {
                        if (K&0x8000) P[0]=sColor;
                        if (K&0x4000) P[1]=sColor;
                        if (K&0x2000) P[2]=sColor;
                        if (K&0x1000) P[3]=sColor;
                        if (K&0x0800) P[4]=sColor;
                        if (K&0x0400) P[5]=sColor;
                        if (K&0x0200) P[6]=sColor;
                        if (K&0x0100) P[7]=sColor;
                    }
                    if(K&0x00FF)
                    {
                        if (K&0x0080) P[8]=sColor;
                        if (K&0x0040) P[9]=sColor;
                        if (K&0x0020) P[10]=sColor;
                        if (K&0x0010) P[11]=sColor;
                        if (K&0x0008) P[12]=sColor;
                        if (K&0x0004) P[13]=sColor;
                        if (K&0x0002) P[14]=sColor;
                        if (K&0x0001) P[15]=sColor;
                    }
                }
            }
        }
    }
}

//---------------------------------------------------------------------------
// Refresh line Y (0..191) of SCREEN0, including sprites in this line
void _TMS9928A_mode0(unsigned char uY) {
    unsigned char X,K,Offset,FC,BC=0;
    unsigned char *P;
    unsigned char *T;
    unsigned char *PGT;
    unsigned int I;

    P  = cv_display
        + TVW*(uY+(TVH-192)/2)
        + TVW/2-128+8;

    if(!TMS9918_ScreenON)
        for(X=0;X<240;X++) *P++=BC;
    else
    {
        BC=tms.BGColor;
        FC=tms.FGColor;
        Offset=(uY & 0x07);

        PGT = tms.ChrGen+Offset;

        // 0x80 before 0x40 to avoid pb
        if (tms.VR[0]&2)
        {
            if (uY >= 0x80)
            {
                switch (tms.VR[4]&3)
                {
                case 0: break;
                case 1: PGT+=0x1000; break;
                case 2: break; //PGT-=0x800; break;
                case 3: PGT+=0x1000; break; //PGT+=0x800; break;
                }
            }
            else if (uY >= 0x40)
            {
                if (tms.VR[4]&2) PGT+=0x800;
            }
        }
        T=tms.ChrTab+(uY>>3)*40;
        for (X=0;X<40;X++)
        {
            I = ((int)*T<<3);
            K=PGT[I];
            P[0]=K&0x80? FC:BC;P[1]=K&0x40? FC:BC;
            P[2]=K&0x20? FC:BC;P[3]=K&0x10? FC:BC;
            P[4]=K&0x08? FC:BC;P[5]=K&0x04? FC:BC;
            P+=6;T++;
        }
    }

    // Refresh screen border
    RefreshBorder(uY);
}

//---------------------------------------------------------------------------
// Refresh line Y (0..191) of SCREEN1, including sprites in this line
void _TMS9928A_mode1(unsigned char uY) {
    unsigned char X,K, Offset,FC,BC;
    unsigned int J;
    unsigned char *T;
    unsigned char *P;

    P  = cv_display + TVW*(uY+(TVH-192)/2) + TVW/2-128;

    if(!TMS9918_ScreenON)
    {
        BC=tms.BGColor;
        for (J=0;J<256;J++) *P++=BC;
    }
    else
    {
        T=tms.ChrTab+((uY & 0xF8)<<2);
        Offset=uY & 0x07;

        for(X=0;X<32;X++)
        {
            K=*T;
            BC=tms.ColTab[K>>3];
            K=tms.ChrGen[((int)K<<3)+Offset];
            FC=tms.IdxPal[BC>>4];
            BC=tms.IdxPal[BC&0x0F];
            P[0]=K&0x80? FC:BC;P[1]=K&0x40? FC:BC;
            P[2]=K&0x20? FC:BC;P[3]=K&0x10? FC:BC;
            P[4]=K&0x08? FC:BC;P[5]=K&0x04? FC:BC;
            P[6]=K&0x02? FC:BC;P[7]=K&0x01? FC:BC;
            P+=8;T++;
        }
        RefreshSprites(uY);
    }

    // Refresh screen border
    RefreshBorder(uY);
}

//---------------------------------------------------------------------------
// Refresh line Y (0..191) of SCREEN2, including sprites in this line
void _TMS9928A_mode2(unsigned char uY) {
    unsigned int X,K,J, FC,BC,Offset;
    unsigned char *T;
    unsigned char *PGT,*CLT;
    unsigned int I;
    unsigned char *P;

    P  = cv_display + TVW*(uY+(TVH-192)/2) + TVW/2-128;

    if (!TMS9918_ScreenON)
    {
        BC=tms.BGColor;
        for (J=0;J<256;J++) *P++=BC;
    }
    else
    {
        Offset=uY&0x07;
        PGT = tms.ChrGen+Offset;
        CLT = tms.ColTab+Offset;

        // 0x80 before 0x40 to avoid pb
        if (uY >= 0x80)
        {
            switch (tms.VR[4]&3)
            {
            case 0: break;
            case 1: PGT+=0x1000; break;
            case 2: break; //PGT-=0x800; break;
            case 3: PGT+=0x1000; break; //PGT+=0x800; break;
            }
            switch (tms.VR[3]&0x60)
            {
            case 0: break;
            case 0x20: CLT+=0x1000; break;
            case 0x40: break; //CLT-=0x800; break;
            case 0x60: CLT+=0x1000; break; //CLT+=0x800; break;
            }
        }
        else if (uY >= 0x40)
        {
            if (tms.VR[4]&2) PGT+=0x800;
            if (tms.VR[3]&0x40) CLT+=0x800;
        }
        T = tms.ChrTab + ((uY & 0xF8) << 2);

        for(X=0;X<32;X++)
        {
            I=((int)*T<<3);

            K = PGT[I];
            BC= tms.IdxPal[CLT[I]&0x0F];
            FC= tms.IdxPal[CLT[I]>>4];

            P[0] = K & 0x80? FC:BC;
            P[1] = K & 0x40? FC:BC;
            P[2] = K & 0x20? FC:BC;
            P[3] = K & 0x10? FC:BC;
            P[4] = K & 0x08? FC:BC;
            P[5] = K & 0x04? FC:BC;
            P[6] = K & 0x02? FC:BC;
            P[7] = K & 0x01? FC:BC;
            P+=8;
            T++;
        }
        RefreshSprites(uY);
    }

    // Refresh screen border
    RefreshBorder(uY);
}

//---------------------------------------------------------------------------
// Refresh line Y (0..191) of SCREEN3, including sprites in this line
void _TMS9928A_mode3(unsigned char uY) {
    unsigned char X,K,Offset;
    unsigned char *P,*T;
    unsigned char *PGT;
    unsigned int I,BC,J;

    P  = cv_display + TVW*(uY+(TVH-192)/2) + TVW/2-128;

    if(!TMS9918_ScreenON)
    {
        BC=tms.BGColor;
        for (J=0;J<256;J++) *P++=BC;
    }
    else {
        Offset=(uY&0x1C)>>2;
        PGT = tms.ChrGen+Offset;

        if (tms.VR[0]&2)
        {
            if (uY >= 0x80)
            {
                switch (tms.VR[4]&3)
                {
                case 0: break;
                case 1: PGT+=0x1000; break;
                case 2: break;
                case 3: PGT+=0x1000; break;
                }
            }
            else if (uY >= 0x40)
            {
                if (tms.VR[4]&2) PGT+=0x800;
            }
        }

        T=tms.ChrTab+((int)(uY&0xF8)<<2);
        for(X=0;X<32;X++)
        {
            I = ((int)*T<<3);
            K=PGT[I];
            P[0]=P[1]=P[2]=P[3]=tms.IdxPal[K>>4];
            P[4]=P[5]=P[6]=P[7]=tms.IdxPal[K&0x0F];
            P+=8;T++;
        }
        RefreshSprites(uY);
    }

    // Refresh screen border
    RefreshBorder(uY);
}

// ----------------------------------------------------------------------------------------
// Call this routine on every scanline to update the screen buffer.
unsigned char tms9918_loop(void) {
    unsigned char bIRQ;

    // No IRQ yet
    bIRQ=0;

    // Increment scanline
    if(++tms.CurLine>=tms.ScanLines) tms.CurLine=0;

    if ((tms.CurLine >= TMS9918_START_LINE) && (tms.CurLine < TMS9918_END_LINE))
       {

         (SCR[tms.Mode].Refresh)(tms.CurLine - TMS9918_START_LINE);
         _push_cv_scanline((int)(tms.CurLine - TMS9918_START_LINE));
       }

    // ======= EINDE HOOK =======

// einde van frame
if (tms.CurLine == TMS9918_END_LINE) {
    if (tms.UCount >= 100) tms.UCount -= 100;
    tms.UCount += TMS9918_DRAWFRAMES;

    // IRQ bij 0->1 transitie van VBlank én IRQ enabled
    if (TMS9918_VBlankON && !(tms.SR & TMS9918_STAT_VBLANK)) {
        bIRQ = 1;
    }

    // sprite overlap vlaggen (ok)
    if (!(tms.SR & TMS9918_STAT_OVRLAP))
        if (CheckSprites()) tms.SR |= TMS9918_STAT_OVRLAP;

    // VBlank flag zetten
    tms.SR |= TMS9918_STAT_VBLANK;

    vb_present_frame(); // jouw frame klaar signaal
}


    // Return IRQ (1) of niet (0)
    return(bIRQ);
}

// tms9928a.c
BYTE ReadStatus9918(void)
{
    BYTE s = tms.SR;

    // statusbits wissen bij read
    tms.SR &= ~(TMS9918_STAT_VBLANK | TMS9918_STAT_5THSPR | TMS9918_STAT_OVRLAP);

    // IRQ-lijn laag na status-read (NMI-lijn de-asserten)
    z80_set_irq_line(INPUT_LINE_NMI, CLEAR_LINE);

    // control latch terug naar "first byte"
    tms.VKey = 1;
    return s;
}
