# HG changeset patch
# User sheepluva
# Date 1480769517 -3600
# Node ID c1d83fc8e89470ac26ee3a525ec76dd3015515de
# Parent  966a9739812fdcd6220edefcc12bad1f8759d6f4
copyToXYFromRect: some tweaks

diff -r 966a9739812f -r c1d83fc8e894 hedgewars/uRenderUtils.pas
--- a/hedgewars/uRenderUtils.pas	Sat Dec 03 09:09:16 2016 +0100
+++ b/hedgewars/uRenderUtils.pas	Sat Dec 03 13:51:57 2016 +0100
@@ -149,9 +149,9 @@
 end;
 
 procedure copyToXYFromRect(src, dest: PSDL_Surface; srcX, srcY, srcW, srcH, destX, destY: LongInt);
-var i, j, iX, iY, dX, dY, lX, lY: LongInt;
+var spi, dpi, iX, iY, dX, dY, lX, lY, aT: LongInt;
     srcPixels, destPixels: PLongWordArray;
-    r0, g0, b0, a0, r1, g1, b1, a1: Byte;
+    rD, gD, bD, aD, rT, gT, bT: Byte;
 begin
     SDL_LockSurface(src);
     SDL_LockSurface(dest);
@@ -164,24 +164,51 @@
     dY:= destY - srcY;
 
     // let's figure out where the rectangle we can actually copy ends
-    lX:= ( min( min(srcX + srcW, src^.w), min(destX + srcW + dx, dest^.w) - dx ) ) - 1;
-    lY:= ( min( min(srcY + srcH, src^.h), min(destY + srcH + dy, dest^.h) - dY ) ) - 1;
+    lX:= ( min( min(srcX + srcW, src^.w), min(destX + srcW, dest^.w) - dx ) ) - 1;
+    lY:= ( min( min(srcY + srcH, src^.h), min(destY + srcH, dest^.h) - dY ) ) - 1;
 
     for iX:= srcX to lX do
     for iY:= srcY to lY do
         begin
-        i:= (iY + dY) * dest^.w + (iX + dX);
-        j:= iY * src^.w  + iX;
-        if srcPixels^[j] and AMask <> 0 then
+        // src pixel index
+        spi:= iY * src^.w  + iX;
+        // dest pixel index
+        dpi:= (iY + dY) * dest^.w + (iX + dX);
+
+        // get src alpha (and set it as target alpha for now)
+        aT:= (srcPixels^[spi] and AMask) shr AShift;
+
+        // src pixel opaque?
+        if aT = 255 then
             begin
-            SDL_GetRGBA(destPixels^[i], dest^.format, @r0, @g0, @b0, @a0);
-            SDL_GetRGBA(srcPixels^[j], src^.format, @r1, @g1, @b1, @a1);
-            r0:= (r0 * (255 - LongInt(a1)) + r1 * LongInt(a1)) div 255;
-            g0:= (g0 * (255 - LongInt(a1)) + g1 * LongInt(a1)) div 255;
-            b0:= (b0 * (255 - LongInt(a1)) + b1 * LongInt(a1)) div 255;
-            a0:= a0 + ((255 - LongInt(a0)) * a1 div 255);
-            destPixels^[i]:= SDL_MapRGBA(dest^.format, r0, g0, b0, a0);
+            // just copy full pixel
+            destPixels^[dpi]:= srcPixels^[spi];
+            continue;
             end;
+
+        // get dst alpha (without shift for now)
+        aD:= (destPixels^[dpi] and AMask) shr AShift;
+
+        // dest completely transparent?
+        if aD = 0 then
+            begin
+            // just copy src pixel
+            destPixels^[dpi]:= srcPixels^[spi];
+            continue;
+            end;
+
+        // looks like some blending is necessary
+
+        // set color of target RGB to src for now
+        SDL_GetRGB(srcPixels^[spi],  src^.format,  @rT, @gT, @bT);
+        SDL_GetRGB(destPixels^[dpi], dest^.format, @rD, @gD, @bD);
+        // note: this is not how to correctly blend RGB, just sayin' (R,G,B are not linear...)
+        rT:= (rD * (255 - aT) + rT * aT) div 255;
+        gT:= (gD * (255 - aT) + gT * aT) div 255;
+        bT:= (bD * (255 - aT) + bT * aT) div 255;
+        aT:= aD + ((255 - LongInt(aD)) * aT div 255);
+
+        destPixels^[dpi]:= SDL_MapRGBA(dest^.format, rT, gT, bT, aT);
         end;
 
     SDL_UnlockSurface(src);
@@ -190,7 +217,7 @@
 
 procedure DrawSprite2Surf(sprite: TSprite; dest: PSDL_Surface; x,y: LongInt); inline;
 begin
-    DrawSpriteFrame2Surf(sprite, dest, x, y, 0);
+   DrawSpriteFrame2Surf(sprite, dest, x, y, 0);
 end;
 
 procedure DrawSpriteFrame2Surf(sprite: TSprite; dest: PSDL_Surface; x,y,frame: LongInt);