Improves the implementation of global composite operation.

This commit updates the implmentation of global composite operation to follow the advices described at c4b865796d (r74248556)

src/nanovg.c

@@ -66,6 +66,7 @@ enum NVGpointFlags
 };
 
 struct NVGstate {
+	NVGcompositeOperationState compositeOperation;
 	NVGpaint fill;
 	NVGpaint stroke;
 	float strokeWidth;
@@ -203,6 +204,79 @@ static void nvg__setDevicePixelRatio(NVGcontext* ctx, float ratio)
 	ctx->devicePxRatio = ratio;
 }
 
+static NVGcompositeOperationState nvg__compositeOperationState(int op)
+{
+	int sfactor, dfactor;
+
+	if (op == NVG_SOURCE_OVER)
+	{
+		sfactor = NVG_ONE;
+		dfactor = NVG_ONE_MINUS_SRC_ALPHA;
+	}
+	else if (op == NVG_SOURCE_IN)
+	{
+		sfactor = NVG_DST_ALPHA;
+		dfactor = NVG_ZERO;
+	}
+	else if (op == NVG_SOURCE_OUT)
+	{
+		sfactor = NVG_ONE_MINUS_DST_ALPHA;
+		dfactor = NVG_ZERO;
+	}
+	else if (op == NVG_ATOP)
+	{
+		sfactor = NVG_DST_ALPHA;
+		dfactor = NVG_ONE_MINUS_SRC_ALPHA;
+	}
+	else if (op == NVG_DESTINATION_OVER)
+	{
+		sfactor = NVG_ONE_MINUS_DST_ALPHA;
+		dfactor = NVG_ONE;
+	}
+	else if (op == NVG_DESTINATION_IN)
+	{
+		sfactor = NVG_ZERO;
+		dfactor = NVG_SRC_ALPHA;
+	}
+	else if (op == NVG_DESTINATION_OUT)
+	{
+		sfactor = NVG_ZERO;
+		dfactor = NVG_ONE_MINUS_SRC_ALPHA;
+	}
+	else if (op == NVG_DESTINATION_ATOP)
+	{
+		sfactor = NVG_ONE_MINUS_DST_ALPHA;
+		dfactor = NVG_SRC_ALPHA;
+	}
+	else if (op == NVG_LIGHTER)
+	{
+		sfactor = NVG_ONE;
+		dfactor = NVG_ONE;
+	}
+	else if (op == NVG_COPY)
+	{
+		sfactor = NVG_ONE;
+		dfactor = NVG_ZERO;
+	}
+	else if (op == NVG_XOR)
+	{
+		sfactor = NVG_ONE_MINUS_DST_ALPHA;
+		dfactor = NVG_ONE_MINUS_SRC_ALPHA;
+	}
+
+	NVGcompositeOperationState state;
+	state.srcRGB = sfactor;
+	state.dstRGB = dfactor;
+	state.srcAlpha = sfactor;
+	state.dstAlpha = dfactor;
+	return state;
+}
+
+static NVGstate* nvg__getState(NVGcontext* ctx)
+{
+	return &ctx->states[ctx->nstates-1];
+}
+
 NVGcontext* nvgCreateInternal(NVGparams* params)
 {
 	FONSparams fontParams;
@@ -310,7 +384,8 @@ void nvgCancelFrame(NVGcontext* ctx)
 
 void nvgEndFrame(NVGcontext* ctx)
 {
-	ctx->params.renderFlush(ctx->params.userPtr);
+	NVGstate* state = nvg__getState(ctx);
+	ctx->params.renderFlush(ctx->params.userPtr, state->compositeOperation);
 	if (ctx->fontImageIdx != 0) {
 		int fontImage = ctx->fontImages[ctx->fontImageIdx];
 		int i, j, iw, ih;
@@ -338,25 +413,6 @@ void nvgEndFrame(NVGcontext* ctx)
 	}
 }
 
-NVGcompositeOperation nvgBlendFunc(int sfactor, int dfactor)
-{
-	return nvgBlendFuncSeparate(sfactor, dfactor, sfactor, dfactor);
-}
-
-NVGcompositeOperation nvgBlendFuncSeparate(int srcRGB, int dstRGB, int srcAlpha, int dstAlpha)
-{
-	NVGcompositeOperation operation;
-	operation.srcRGB = srcRGB;
-	operation.dstRGB = dstRGB;
-	operation.srcAlpha = srcAlpha;
-	operation.dstAlpha = dstAlpha;
-	return operation;
-}
-
-void nvgGlobalCompositeOperation(NVGcontext* ctx, NVGcompositeOperation op) {
-	ctx->params.renderCompositeOperation(ctx->params.userPtr, op);
-}
-
 NVGcolor nvgRGB(unsigned char r, unsigned char g, unsigned char b)
 {
 	return nvgRGBA(r,g,b,255);
@@ -452,12 +508,6 @@ NVGcolor nvgHSLA(float h, float s, float l, unsigned char a)
 	return col;
 }
 
-
-static NVGstate* nvg__getState(NVGcontext* ctx)
-{
-	return &ctx->states[ctx->nstates-1];
-}
-
 void nvgTransformIdentity(float* t)
 {
 	t[0] = 1.0f; t[1] = 0.0f;
@@ -590,6 +640,7 @@ void nvgReset(NVGcontext* ctx)
 
 	nvg__setPaintColor(&state->fill, nvgRGBA(255,255,255,255));
 	nvg__setPaintColor(&state->stroke, nvgRGBA(0,0,0,255));
+	state->compositeOperation = nvg__compositeOperationState(NVG_SOURCE_OVER);
 	state->strokeWidth = 1.0f;
 	state->miterLimit = 10.0f;
 	state->lineCap = NVG_BUTT;
@@ -958,6 +1009,30 @@ void nvgResetScissor(NVGcontext* ctx)
 	state->scissor.extent[1] = -1.0f;
 }
 
+// Global composite operation.
+void nvgGlobalCompositeOperation(NVGcontext* ctx, int op)
+{
+	NVGstate* state = nvg__getState(ctx);
+	state->compositeOperation = nvg__compositeOperationState(op);
+}
+
+void nvgGlobalCompositeBlendFunc(NVGcontext* ctx, int sfactor, int dfactor)
+{
+	nvgGlobalCompositeBlendFuncSeparate(ctx, sfactor, dfactor, sfactor, dfactor);
+}
+
+void nvgGlobalCompositeBlendFuncSeparate(NVGcontext* ctx, int srcRGB, int dstRGB, int srcAlpha, int dstAlpha)
+{
+	NVGcompositeOperationState op;
+	op.srcRGB = srcRGB;
+	op.dstRGB = dstRGB;
+	op.srcAlpha = srcAlpha;
+	op.dstAlpha = dstAlpha;
+
+	NVGstate* state = nvg__getState(ctx);
+	state->compositeOperation = op;
+}
+
 static int nvg__ptEquals(float x1, float y1, float x2, float y2, float tol)
 {
 	float dx = x2 - x1;

src/nanovg.h

@@ -97,26 +97,27 @@ enum NVGblendFactor {
 	NVG_SRC_ALPHA_SATURATE = 1<<10,
 };
 
-struct NVGcompositeOperation {
+struct NVGcompositeOperationState {
 	int srcRGB;
 	int dstRGB;
 	int srcAlpha;
 	int dstAlpha;
 };
-typedef struct NVGcompositeOperation NVGcompositeOperation;
-
-// Predefined composite operations.
-#define NVG_SOURCE_OVER nvgBlendFunc(NVG_ONE, NVG_ONE_MINUS_SRC_ALPHA)
-#define NVG_SOURCE_IN nvgBlendFunc(NVG_DST_ALPHA, NVG_ZERO)
-#define NVG_SOURCE_OUT nvgBlendFunc(NVG_ONE_MINUS_DST_ALPHA, NVG_ZERO)
-#define NVG_ATOP nvgBlendFunc(NVG_DST_ALPHA, NVG_ONE_MINUS_SRC_ALPHA)
-#define NVG_DESTINATION_OVER nvgBlendFunc(NVG_ONE_MINUS_DST_ALPHA, NVG_ONE)
-#define NVG_DESTINATION_IN nvgBlendFunc(NVG_ZERO, NVG_SRC_ALPHA)
-#define NVG_DESTINATION_OUT nvgBlendFunc(NVG_ZERO, NVG_ONE_MINUS_SRC_ALPHA)
-#define NVG_DESTINATION_ATOP nvgBlendFunc(NVG_ONE_MINUS_DST_ALPHA, NVG_SRC_ALPHA)
-#define NVG_LIGHTER nvgBlendFunc(NVG_ONE, NVG_ONE)
-#define NVG_COPY nvgBlendFunc(NVG_ONE, NVG_ZERO)
-#define NVG_XOR nvgBlendFunc(NVG_ONE_MINUS_DST_ALPHA NVG_ONE_MINUS_SRC_ALPHA)
+typedef struct NVGcompositeOperationState NVGcompositeOperationState;
+
+enum NVGcompositeOperation {
+	NVG_SOURCE_OVER,
+	NVG_SOURCE_IN,
+	NVG_SOURCE_OUT,
+	NVG_ATOP,
+	NVG_DESTINATION_OVER,
+	NVG_DESTINATION_IN,
+	NVG_DESTINATION_OUT,
+	NVG_DESTINATION_ATOP,
+	NVG_LIGHTER,
+	NVG_COPY,
+	NVG_XOR,
+};
 
 struct NVGglyphPosition {
 	const char* str;	// Position of the glyph in the input string.
@@ -162,17 +163,16 @@ void nvgEndFrame(NVGcontext* ctx);
 // Composite operation
 //
 // Composite operation in NanoVG works between frames. The default composite
-// operation of NanoVG is NVG_SOURCE_OVER, and the value is reset whenever
-// calling nvgBeginFrame().
+// operation of NanoVG is NVG_SOURCE_OVER.
 
-// Creates a composite operation with custom pixel arithmetic. The parameters should be one of NVGblendFactor.
-NVGcompositeOperation nvgBlendFunc(int sfactor, int dfactor);
+// Sets the composite operation. The op parameter should be one of NVGcompositeOperation.
+void nvgGlobalCompositeOperation(NVGcontext* ctx, int op);
 
-// Creates a composite operation with custom pixel arithmetic for RGB and alpha components separately. The parameters should be one of NVGblendFactor.
-NVGcompositeOperation nvgBlendFuncSeparate(int srcRGB, int dstRGB, int srcAlpha, int dstAlpha);
+// Sets the composite operation with custom pixel arithmetic. The parameters should be one of NVGblendFactor.
+void nvgGlobalCompositeBlendFunc(NVGcontext* ctx, int sfactor, int dfactor);
 
-// Sets the composite operation for the current frame. This function should be called between nvgBeginFrame() and nvgEndFrame(). The default composite operation of NanoVG is NVG_SOURCE_OVER.
-void nvgGlobalCompositeOperation(NVGcontext* ctx, NVGcompositeOperation op);
+// Sets the composite operation with custom pixel arithmetic for RGB and alpha components separately. The parameters should be one of NVGblendFactor.
+void nvgGlobalCompositeBlendFuncSeparate(NVGcontext* ctx, int srcRGB, int dstRGB, int srcAlpha, int dstAlpha);
 
 //
 // Color utils
@@ -641,8 +641,7 @@ struct NVGparams {
 	int (*renderGetTextureSize)(void* uptr, int image, int* w, int* h);
 	void (*renderViewport)(void* uptr, int width, int height, float devicePixelRatio);
 	void (*renderCancel)(void* uptr);
-	void (*renderCompositeOperation)(void* uptr, NVGcompositeOperation op);
-	void (*renderFlush)(void* uptr);
+	void (*renderFlush)(void* uptr, NVGcompositeOperationState compositeOperation);
 	void (*renderFill)(void* uptr, NVGpaint* paint, NVGscissor* scissor, float fringe, const float* bounds, const NVGpath* paths, int npaths);
 	void (*renderStroke)(void* uptr, NVGpaint* paint, NVGscissor* scissor, float fringe, float strokeWidth, const NVGpath* paths, int npaths);
 	void (*renderTriangles)(void* uptr, NVGpaint* paint, NVGscissor* scissor, const NVGvertex* verts, int nverts);

src/nanovg_gl.h

@@ -219,7 +219,6 @@ struct GLNVGfragUniforms {
 typedef struct GLNVGfragUniforms GLNVGfragUniforms;
 
 struct GLNVGcontext {
-	NVGcompositeOperation compositeOperation;
 	GLNVGshader shader;
 	GLNVGtexture* textures;
 	float view[2];
@@ -945,7 +944,6 @@ static void glnvg__setUniforms(GLNVGcontext* gl, int uniformOffset, int image)
 static void glnvg__renderViewport(void* uptr, int width, int height, float devicePixelRatio)
 {
 	GLNVGcontext* gl = (GLNVGcontext*)uptr;
-	gl->compositeOperation = NVG_SOURCE_OVER;  // resets composition
 	gl->view[0] = (float)width;
 	gl->view[1] = (float)height;
 }
@@ -1100,18 +1098,12 @@ static GLenum glnvg_convertBlendFuncFactor(int factor)
 		return GL_SRC_ALPHA_SATURATE;
 }
 
-static void glnvg__blendCompositeOperation(NVGcompositeOperation operation)
+static void glnvg__blendCompositeOperation(NVGcompositeOperationState op)
 {
-	glBlendFuncSeparate(glnvg_convertBlendFuncFactor(operation.srcRGB), glnvg_convertBlendFuncFactor(operation.dstRGB), glnvg_convertBlendFuncFactor(operation.srcAlpha), glnvg_convertBlendFuncFactor(operation.dstAlpha));
+	glBlendFuncSeparate(glnvg_convertBlendFuncFactor(op.srcRGB), glnvg_convertBlendFuncFactor(op.dstRGB), glnvg_convertBlendFuncFactor(op.srcAlpha), glnvg_convertBlendFuncFactor(op.dstAlpha));
 }
 
-static void glnvg__renderCompositeOperation(void* uptr, NVGcompositeOperation op)
-{
-	GLNVGcontext* gl = (GLNVGcontext*)uptr;
-	gl->compositeOperation = op;
-}
-
-static void glnvg__renderFlush(void* uptr)
+static void glnvg__renderFlush(void* uptr, NVGcompositeOperationState compositeOperation)
 {
 	GLNVGcontext* gl = (GLNVGcontext*)uptr;
 	int i;
@@ -1121,7 +1113,7 @@ static void glnvg__renderFlush(void* uptr)
 		// Setup require GL state.
 		glUseProgram(gl->shader.prog);
 
-		glnvg__blendCompositeOperation(gl->compositeOperation);
+		glnvg__blendCompositeOperation(compositeOperation);
 		glEnable(GL_CULL_FACE);
 		glCullFace(GL_BACK);
 		glFrontFace(GL_CCW);
@@ -1512,7 +1504,6 @@ NVGcontext* nvgCreateGLES3(int flags)
 	params.renderGetTextureSize = glnvg__renderGetTextureSize;
 	params.renderViewport = glnvg__renderViewport;
 	params.renderCancel = glnvg__renderCancel;
-	params.renderCompositeOperation = glnvg__renderCompositeOperation;
 	params.renderFlush = glnvg__renderFlush;
 	params.renderFill = glnvg__renderFill;
 	params.renderStroke = glnvg__renderStroke;