From 0c8e698b6e412a8ef98bb348567b4d9511614bb1 Mon Sep 17 00:00:00 2001
From: Martin Fouilleul <martinfouilleul@gmail.com>
Date: Thu, 27 Jul 2023 16:10:30 +0200
Subject: [PATCH] [mtl canvas] don't trigger a new batch when setting the
 current image to nil (avoids creating a lot of batches when we just alternate
 between the same image and no image, eg painting multiple instances of the
 same image with a stroked border)

---
 src/mtl_renderer.h     |  1 +
 src/mtl_renderer.m     | 34 ++++++++++++++++++++--------------
 src/mtl_renderer.metal |  3 +--
 3 files changed, 22 insertions(+), 16 deletions(-)

diff --git a/src/mtl_renderer.h b/src/mtl_renderer.h
index 788e1df..94e8910 100644
--- a/src/mtl_renderer.h
+++ b/src/mtl_renderer.h
@@ -23,6 +23,7 @@ typedef struct mg_mtl_path
 	vector_float4 color;
 	vector_float4 box;
 	vector_float4 clip;
+	int texture;
 } mg_mtl_path;
 
 typedef enum {
diff --git a/src/mtl_renderer.m b/src/mtl_renderer.m
index 8cd5811..efa956f 100644
--- a/src/mtl_renderer.m
+++ b/src/mtl_renderer.m
@@ -249,6 +249,12 @@ void mg_mtl_encode_path(mg_mtl_canvas_backend* backend, mg_primitive* primitive,
 		path->uvTransform = simd_matrix(simd_make_float3(uvTransform.m[0]/scale, uvTransform.m[3]/scale, 0),
 		                                simd_make_float3(uvTransform.m[1]/scale, uvTransform.m[4]/scale, 0),
 		                                simd_make_float3(uvTransform.m[2], uvTransform.m[5], 1));
+
+		path->texture = 1;
+	}
+	else
+	{
+		path->texture = 0;
 	}
 
 	int nTilesX = ((path->box.z - path->box.x)*scale - 1) / MG_MTL_TILE_SIZE + 1;
@@ -1084,14 +1090,11 @@ void mg_mtl_render_batch(mg_mtl_canvas_backend* backend,
 
 		[rasterEncoder setTexture:backend->outTexture atIndex:0];
 
-		int useTexture = 0;
 		if(image)
 		{
 			mg_mtl_image_data* mtlImage = (mg_mtl_image_data*)image;
 			[rasterEncoder setTexture: mtlImage->texture atIndex: 1];
-			useTexture = 1;
 		}
-		[rasterEncoder setBytes: &useTexture length:sizeof(int) atIndex: 9];
 
 		MTLSize rasterGridSize = MTLSizeMake(viewportSize.x, viewportSize.y, 1);
 		MTLSize rasterGroupSize = MTLSizeMake(MG_MTL_TILE_SIZE, MG_MTL_TILE_SIZE, 1);
@@ -1233,20 +1236,23 @@ void mg_mtl_canvas_render(mg_canvas_backend* interface,
 	{
 		mg_primitive* primitive = &primitives[primitiveIndex];
 
-		if(primitiveIndex && (primitive->attributes.image.h != currentImage.h))
+		if(primitive->attributes.image.h != 0)
 		{
-			mg_image_data* imageData = mg_image_data_from_handle(currentImage);
+			if(primitiveIndex && (primitive->attributes.image.h != currentImage.h))
+			{
+				mg_image_data* imageData = mg_image_data_from_handle(currentImage);
 
-			mg_mtl_render_batch(backend,
-			                    surface,
-			                    imageData,
-			                    tileSize,
-			                    nTilesX,
-			                    nTilesY,
-			                    viewportSize,
-			                    scale);
+				mg_mtl_render_batch(backend,
+				                    surface,
+				                    imageData,
+				                    tileSize,
+				                    nTilesX,
+				                    nTilesY,
+				                    viewportSize,
+				                    scale);
+			}
+			currentImage = primitive->attributes.image;
 		}
-		currentImage = primitive->attributes.image;
 
 		if(primitive->path.count)
 		{
diff --git a/src/mtl_renderer.metal b/src/mtl_renderer.metal
index 1013f85..d6d39e2 100644
--- a/src/mtl_renderer.metal
+++ b/src/mtl_renderer.metal
@@ -1512,7 +1512,6 @@ kernel void mtl_raster(const device mg_mtl_screen_tile* screenTilesBuffer [[buff
                        constant int* sampleCountBuffer [[buffer(6)]],
                        device char* logBuffer [[buffer(7)]],
                        device atomic_int* logOffsetBuffer [[buffer(8)]],
-                       constant int* useTexture [[buffer(9)]],
                        texture2d<float, access::write> outTexture [[texture(0)]],
                        texture2d<float> srcTexture [[texture(1)]],
                        uint2  threadGroupCoord [[threadgroup_position_in_grid]],
@@ -1611,7 +1610,7 @@ kernel void mtl_raster(const device mg_mtl_screen_tile* screenTilesBuffer [[buff
 			float4 nextColor = pathBuffer[pathIndex].color;
 			nextColor.rgb *= nextColor.a;
 
-			if(useTexture[0])
+			if(pathBuffer[pathIndex].texture)
 			{
 				constexpr sampler smp(mip_filter::nearest, mag_filter::linear, min_filter::linear);