[mtl canvas] render to an intermediate texture and acquire the drawable and blit to it only at the end of all compute passes

examples/perf_text/main.c

@@ -60,10 +60,10 @@ static const char* TEST_STRING =
 "sit amet, malesuada enim. Mauris ultricies nibh orci.";
 
 
-mg_font create_font()
+mg_font create_font(const char* path)
 {
 	//NOTE(martin): create font
-	str8 fontPath = mp_app_get_resource_path(mem_scratch(), "../resources/OpenSansLatinSubset.ttf");
+	str8 fontPath = mp_app_get_resource_path(mem_scratch(), path);
 	char* fontPathCString = str8_to_cstring(mem_scratch(), fontPath);
 
 	FILE* fontFile = fopen(fontPathCString, "r");
@@ -106,15 +106,26 @@ int main()
 	//NOTE: create surface, canvas and font
 
 	mg_surface surface = mg_surface_create_for_window(window, MG_BACKEND_DEFAULT);
-	mg_surface_swap_interval(surface, 0);
+	mg_surface_swap_interval(surface, 1);
 
 	mg_canvas canvas = mg_canvas_create(surface);
 
-	mg_font font = create_font();
+	const int fontCount = 3;
-	mg_font_extents extents = mg_font_get_extents(font);
+	int fontIndex = 0;
-	f32 fontScale = mg_font_get_scale_for_em_pixels(font, 14);
+	mg_font fonts[fontCount] = {create_font("../resources/OpenSansLatinSubset.ttf"),
+	                            create_font("../resources/CMUSerif-Roman.ttf"),
+	                            create_font("../resources/courier.ttf")};
 
-	f32 lineHeight = fontScale*(extents.ascent + extents.descent + extents.leading);
+	mg_font_extents extents[fontCount];
+	f32 fontScales[fontCount];
+	f32 lineHeights[fontCount];
+
+	for(int i=0; i<fontCount; i++)
+	{
+		extents[i] = mg_font_get_extents(fonts[i]);
+		fontScales[i] = mg_font_get_scale_for_em_pixels(fonts[i], 14);
+		lineHeights[i] = fontScales[i]*(extents[i].ascent + extents[i].descent + extents[i].leading);
+	}
 
 	int codePointCount = utf8_codepoint_count_for_string(STR8((char*)TEST_STRING));
 	u32* codePoints = malloc_array(utf32, codePointCount);
@@ -140,7 +151,7 @@ int main()
 	f32 zoom = 1;
 
 	f32 startX = 10;
-	f32 startY = 10 + lineHeight;
+	f32 startY = 10 + lineHeights[fontIndex];
 
 	while(!mp_should_quit())
 	{
@@ -188,6 +199,14 @@ int main()
 					startY = mousePos.y/zoom - trackY;
 				} break;
 
+				case MP_EVENT_KEYBOARD_KEY:
+				{
+					if(event.key.code == MP_KEY_SPACE && event.key.action == MP_KEY_PRESS)
+					{
+						fontIndex = (fontIndex+1)%fontCount;
+					}
+				} break;
+
 				default:
 					break;
 			}
@@ -219,7 +238,7 @@ int main()
 			mg_set_color_rgba(1, 1, 1, 1);
 			mg_clear();
 
-			mg_set_font(font);
+			mg_set_font(fonts[fontIndex]);
 			mg_set_font_size(14);
 			mg_set_color_rgba(0, 0, 0, 1);
 
@@ -239,12 +258,12 @@ int main()
 				}
 
 				u32 glyphs[512];
-				mg_font_get_glyph_indices(font, (str32){subIndex, codePoints+startIndex}, (str32){512, glyphs});
+				mg_font_get_glyph_indices(fonts[fontIndex], (str32){subIndex, codePoints+startIndex}, (str32){512, glyphs});
 
 				mg_glyph_outlines((str32){subIndex, glyphs});
 				mg_fill();
 
-				textY += lineHeight;
+				textY += lineHeights[fontIndex];
 				mg_move_to(textX, textY);
 				startIndex++;
 
@@ -254,9 +273,9 @@ int main()
 			mg_matrix_pop();
 
 			mg_set_color_rgba(0, 0, 1, 1);
-			mg_set_font(font);
+			mg_set_font(fonts[fontIndex]);
 			mg_set_font_size(14);
-			mg_move_to(10, contentRect.h - 10 - lineHeight);
+			mg_move_to(10, contentRect.h - 10 - lineHeights[fontIndex]);
 
 			str8 text = str8_pushf(mem_scratch(),
 			                      "Test program: %i glyphs, frame time = %fs, fps = %f",
@@ -290,7 +309,10 @@ int main()
 	}
 
 
-	mg_font_destroy(font);
+	for(int i=0; i<fontCount; i++)
+	{
+		mg_font_destroy(fonts[i]);
+	}
 	mg_canvas_destroy(canvas);
 	mg_surface_destroy(surface);
 	mp_window_destroy(window);

src/mtl_canvas.m

@@ -31,6 +31,8 @@ typedef struct mg_mtl_canvas_backend
 	u32 indexBufferOffset;
 	u32 shapeBufferOffset;
 
+	mg_color clearColor;
+
 	// permanent metal resources
 	id<MTLComputePipelineState> tilingPipeline;
 	id<MTLComputePipelineState> sortingPipeline;
@@ -44,7 +46,7 @@ typedef struct mg_mtl_canvas_backend
 	dispatch_semaphore_t bufferSemaphore;
 
 	// textures and buffers
-	id<MTLTexture> framebuffer;
+	id<MTLTexture> backbuffer;
 	id<MTLTexture> outTexture;
 
 	id<MTLBuffer> shapeBuffer[MG_MTL_MAX_BUFFERS_IN_FLIGHT];
@@ -109,6 +111,7 @@ void mg_mtl_canvas_begin(mg_canvas_backend* interface, mg_color clearColor)
 	{
 		return;
 	}
+	backend->clearColor = clearColor;
 
 	backend->vertexBufferOffset = 0;
 	backend->indexBufferOffset = 0;
@@ -121,30 +124,21 @@ void mg_mtl_canvas_begin(mg_canvas_backend* interface, mg_color clearColor)
 
 	@autoreleasepool
 	{
-		if(surface->commandBuffer == nil || surface->drawable == nil)
+		MTLClearColor mtlClearColor = MTLClearColorMake(clearColor.r,
-		{
+				                                        clearColor.g,
-			mg_mtl_surface_acquire_drawable_and_command_buffer(surface);
+				                                        clearColor.b,
-		}
+				                                        clearColor.a);
-		if(surface->drawable != nil)
-		{
-			backend->framebuffer = surface->drawable.texture;
-
-			MTLClearColor mtlClearColor = MTLClearColorMake(clearColor.r, clearColor.g, clearColor.b, clearColor.a);
 
 		MTLRenderPassDescriptor* renderPassDescriptor = [MTLRenderPassDescriptor renderPassDescriptor];
-			renderPassDescriptor.colorAttachments[0].texture = surface->drawable.texture;
+		renderPassDescriptor.colorAttachments[0].texture = backend->backbuffer;
 		renderPassDescriptor.colorAttachments[0].loadAction = MTLLoadActionClear;
 		renderPassDescriptor.colorAttachments[0].clearColor = mtlClearColor;
 		renderPassDescriptor.colorAttachments[0].storeAction = MTLStoreActionStore;
 
 		id<MTLRenderCommandEncoder> renderEncoder = [surface->commandBuffer renderCommandEncoderWithDescriptor:renderPassDescriptor];
+		renderEncoder.label = @"clear pass";
 		[renderEncoder endEncoding];
 	}
-		else
-		{
-			backend->framebuffer = nil;
-		}
-	}
 }
 
 void mg_mtl_canvas_end(mg_canvas_backend* interface)
@@ -156,6 +150,32 @@ void mg_mtl_canvas_end(mg_canvas_backend* interface)
 	{
 		@autoreleasepool
 		{
+			mg_mtl_surface_acquire_drawable_and_command_buffer(surface);
+			if(surface->drawable != nil)
+			{
+				f32 scale = surface->mtlLayer.contentsScale;
+				MTLViewport viewport = {backend->viewPort.x * scale,
+		                        		backend->viewPort.y * scale,
+		                        		backend->viewPort.w * scale,
+		                        		backend->viewPort.h * scale,
+		                        		0,
+		                        		1};
+
+				MTLRenderPassDescriptor* renderPassDescriptor = [MTLRenderPassDescriptor renderPassDescriptor];
+				renderPassDescriptor.colorAttachments[0].texture = surface->drawable.texture;
+				renderPassDescriptor.colorAttachments[0].loadAction = MTLLoadActionLoad;
+				renderPassDescriptor.colorAttachments[0].storeAction = MTLStoreActionStore;
+
+				id<MTLRenderCommandEncoder> renderEncoder = [surface->commandBuffer renderCommandEncoderWithDescriptor:renderPassDescriptor];
+				renderEncoder.label = @"blit pass";
+				[renderEncoder setViewport: viewport];
+				[renderEncoder setRenderPipelineState: backend->renderPipeline];
+				[renderEncoder setFragmentTexture: backend->backbuffer atIndex: 0];
+				[renderEncoder drawPrimitives: MTLPrimitiveTypeTriangle
+			 		vertexStart: 0
+			 		vertexCount: 3 ];
+				[renderEncoder endEncoding];
+
 				[surface->commandBuffer addCompletedHandler:^(id<MTLCommandBuffer> commandBuffer)
 					{
 						dispatch_semaphore_signal(backend->bufferSemaphore);
@@ -163,6 +183,7 @@ void mg_mtl_canvas_end(mg_canvas_backend* interface)
 				];
 			}
 		}
+    }
 }
 
 void mg_mtl_canvas_draw_batch(mg_canvas_backend* interface, mg_image_data* image, u32 shapeCount, u32 vertexCount, u32 indexCount)
@@ -170,7 +191,7 @@ void mg_mtl_canvas_draw_batch(mg_canvas_backend* interface, mg_image_data* image
 	mg_mtl_canvas_backend* backend = (mg_mtl_canvas_backend*)interface;
 	mg_mtl_surface* surface = mg_mtl_canvas_get_surface(backend);
 
-	if(!surface || (backend->framebuffer == nil))
+	if(!surface || (backend->backbuffer == nil))
 	{
 		return;
 	}
@@ -264,7 +285,7 @@ void mg_mtl_canvas_draw_batch(mg_canvas_backend* interface, mg_image_data* image
 		[drawEncoder endEncoding];
 
 		//-----------------------------------------------------------
-		//NOTE(martin): blit texture to framebuffer
+		//NOTE(martin): blit texture to backbuffer
 		//-----------------------------------------------------------
 
 		MTLViewport viewport = {backend->viewPort.x * scale,
@@ -275,7 +296,7 @@ void mg_mtl_canvas_draw_batch(mg_canvas_backend* interface, mg_image_data* image
 		                        1};
 
 		MTLRenderPassDescriptor* renderPassDescriptor = [MTLRenderPassDescriptor renderPassDescriptor];
-		renderPassDescriptor.colorAttachments[0].texture = backend->framebuffer;
+		renderPassDescriptor.colorAttachments[0].texture = backend->backbuffer;
 		renderPassDescriptor.colorAttachments[0].loadAction = MTLLoadActionLoad;
 		renderPassDescriptor.colorAttachments[0].storeAction = MTLStoreActionStore;
 
@@ -453,6 +474,7 @@ mg_canvas_backend* mg_mtl_canvas_create(mg_surface surface)
 			texDesc.height = drawableSize.height;
 
 			backend->outTexture = [metalSurface->device newTextureWithDescriptor:texDesc];
+			backend->backbuffer = [metalSurface->device newTextureWithDescriptor:texDesc];
 			//TODO(martin): retain ?
 
 			//-----------------------------------------------------------