@@ -22,6 +22,7 @@ - GBA DMA: ROM reads are forced to increment
  - GB Video: Fix loading states while in mode 3
  - GB Video: Only trigger STAT write IRQs when screen is on (fixes mgba.io/i/912)
  - GBA Cheats: Fix PARv3 slide codes (fixes mgba.io/i/919)
+ - GBA Video: OBJWIN can change blend params after OBJ is drawn (fixes mgba.io/i/921)
 Misc:
  - GBA Timer: Use global cycles for timers
  - GBA: Extend oddly-sized ROMs to full address space (fixes mgba.io/i/722)

@@ -156,26 +156,26 @@ if (renderer->spriteCyclesRemaining <= 0) {
 		return 0;
 	}
 
+	int objwinSlowPath = GBARegisterDISPCNTIsObjwinEnable(renderer->dispcnt) && GBAWindowControlGetBlendEnable(renderer->objwin.packed) != GBAWindowControlIsBlendEnable(renderer->currentWindow.packed);
 	int variant = renderer->target1Obj &&
 	              GBAWindowControlIsBlendEnable(renderer->currentWindow.packed) &&
 	              (renderer->blendEffect == BLEND_BRIGHTEN || renderer->blendEffect == BLEND_DARKEN);
-	if (GBAObjAttributesAGetMode(sprite->a) == OBJ_MODE_SEMITRANSPARENT) {
-		int target2 = renderer->target2Bd << 4;
-		target2 |= renderer->bg[0].target2 << (renderer->bg[0].priority);
-		target2 |= renderer->bg[1].target2 << (renderer->bg[1].priority);
-		target2 |= renderer->bg[2].target2 << (renderer->bg[2].priority);
-		target2 |= renderer->bg[3].target2 << (renderer->bg[3].priority);
-		if ((1 << GBAObjAttributesCGetPriority(sprite->c)) <= target2) {
+	if (GBAObjAttributesAGetMode(sprite->a) == OBJ_MODE_SEMITRANSPARENT || objwinSlowPath) {
+		int target2 = renderer->target2Bd;
+		target2 |= renderer->bg[0].target2;
+		target2 |= renderer->bg[1].target2;
+		target2 |= renderer->bg[2].target2;
+		target2 |= renderer->bg[3].target2;
+		if (target2) {
 			flags |= FLAG_REBLEND;
 			variant = 0;
-		} else if (!target2) {
+		} else {
 			flags &= ~FLAG_TARGET_1;
 		}
 	}
 
 	color_t* palette = &renderer->normalPalette[0x100];
 	color_t* objwinPalette = palette;
-	int objwinSlowPath = GBARegisterDISPCNTIsObjwinEnable(renderer->dispcnt) && GBAWindowControlGetBlendEnable(renderer->objwin.packed) != GBAWindowControlIsBlendEnable(renderer->currentWindow.packed);
 
 	if (variant) {
 		palette = &renderer->variantPalette[0x100];

@@ -43,7 +43,7 @@ if (color >= current) {
 		if (current & FLAG_TARGET_1 && color & FLAG_TARGET_2) {
 			color = _mix(renderer->blda, current, renderer->bldb, color);
 		} else {
-			color = (current & 0x00FFFFFF) | (current & FLAG_REBLEND);
+			color = (current & 0x00FFFFFF) | (current & (FLAG_REBLEND | FLAG_OBJWIN));
 		}
 	} else {
 		color = (color & ~FLAG_TARGET_2) | (current & FLAG_OBJWIN);
@@ -59,7 +59,7 @@ if (color >= current) {
 		if (current & FLAG_TARGET_1 && color & FLAG_TARGET_2) {
 			color = _mix(renderer->blda, current, renderer->bldb, color);
 		} else {
-			color = (current & 0x00FFFFFF) | (current & FLAG_REBLEND);
+			color = (current & 0x00FFFFFF) | (current & (FLAG_REBLEND | FLAG_OBJWIN));
 		}
 	} else {
 		color = color & ~FLAG_TARGET_2;
@@ -73,7 +73,7 @@ UNUSED(renderer);
 	if (color < current) {
 		color |= (current & FLAG_OBJWIN);
 	} else {
-		color = (current & 0x00FFFFFF) | (current & FLAG_REBLEND);
+		color = (current & 0x00FFFFFF) | (current & (FLAG_REBLEND | FLAG_OBJWIN));
 	}
 	*pixel = color;
 }
@@ -82,7 +82,7 @@ static inline void _compositeNoBlendNoObjwin(struct GBAVideoSoftwareRenderer* renderer, uint32_t* pixel, uint32_t color,
                                              uint32_t current) {
 	UNUSED(renderer);
 	if (color >= current) {
-		color = (current & 0x00FFFFFF) | (current & FLAG_REBLEND);
+		color = (current & 0x00FFFFFF) | (current & (FLAG_REBLEND | FLAG_OBJWIN));
 	}
 	*pixel = color;
 }

@@ -621,6 +621,14 @@ }
 	}
 	if (softwareRenderer->target1Obj && (softwareRenderer->blendEffect == BLEND_DARKEN || softwareRenderer->blendEffect == BLEND_BRIGHTEN)) {
 		x = 0;
+		uint32_t mask = 0xFF000000 & ~FLAG_OBJWIN;
+		uint32_t match = FLAG_REBLEND;
+		if (GBARegisterDISPCNTIsObjwinEnable(softwareRenderer->dispcnt)) {
+			mask |= FLAG_OBJWIN;
+			if (GBAWindowControlIsBlendEnable(softwareRenderer->objwin.packed)) {
+				match |= FLAG_OBJWIN;
+			}
+		}
 		for (w = 0; w < softwareRenderer->nWindows; ++w) {
 			if (!GBAWindowControlIsBlendEnable(softwareRenderer->windows[w].control.packed)) {
 				continue;
@@ -629,14 +637,14 @@ int end = softwareRenderer->windows[w].endX;
 			if (softwareRenderer->blendEffect == BLEND_DARKEN) {
 				for (; x < end; ++x) {
 					uint32_t color = softwareRenderer->row[x];
-					if ((color & 0xFF000000) == FLAG_REBLEND) {
+					if ((color & mask) == match) {
 						softwareRenderer->row[x] = _darken(color, softwareRenderer->bldy);
 					}
 				}
 			} else if (softwareRenderer->blendEffect == BLEND_BRIGHTEN) {
 				for (; x < end; ++x) {
 					uint32_t color = softwareRenderer->row[x];
-					if ((color & 0xFF000000) == FLAG_REBLEND) {
+					if ((color & mask) == match) {
 						softwareRenderer->row[x] = _brighten(color, softwareRenderer->bldy);
 					}
 				}