Fix #103398: Fix Icon sampler initialization in Metal backend.

Resolves issue with nearest filtering on UI Icons. Note that as
Metal does not support LOD bias as a parameter on a sampler
object, the original code has been modified to perform LOD
biasing at the shader level.

As GPU_SAMPLER_ICON is not  widely used, it is more
efficient to apply directly to the  affected shaders, rather
than workaround passing in the sampler LOD bias as a
separate value e.g. uniform or push constant.

Original PR feedback addressed to also refactor ICON
shaders to use consistent style for single and multi
Icon rendering.

Authored by Apple: Michael Parkin-White

Ref #96261
Pull Request #105145

source/blender/editors/interface/interface_icons.cc

@@ -1617,12 +1617,12 @@ static void icon_draw_cache_texture_flush_ex(GPUTexture *texture,
     return;
   }
 
-  GPUShader *shader = GPU_shader_get_builtin_shader(GPU_SHADER_2D_IMAGE_MULTI_RECT_COLOR);
+  GPUShader *shader = GPU_shader_get_builtin_shader(GPU_SHADER_ICON_MULTI);
   GPU_shader_bind(shader);
 
-  const int data_binding = GPU_shader_get_ubo_binding(shader, "multi_rect_data");
+  const int data_binding = GPU_shader_get_ubo_binding(shader, "multi_icon_data");
   GPUUniformBuf *ubo = GPU_uniformbuf_create_ex(
-      sizeof(MultiRectCallData), texture_draw_calls->drawcall_cache, __func__);
+      sizeof(MultiIconCallData), texture_draw_calls->drawcall_cache, __func__);
   GPU_uniformbuf_bind(ubo, data_binding);
 
   const int img_binding = GPU_shader_get_sampler_binding(shader, "image");
@@ -1798,7 +1798,7 @@ static void icon_draw_texture(float x,
   GPU_shader_bind(shader);
 
   const int img_binding = GPU_shader_get_sampler_binding(shader, "image");
-  const int color_loc = GPU_shader_get_builtin_uniform(shader, GPU_UNIFORM_COLOR);
+  const int color_loc = GPU_shader_get_uniform(shader, "finalColor");
   const int rect_tex_loc = GPU_shader_get_uniform(shader, "rect_icon");
   const int rect_geom_loc = GPU_shader_get_uniform(shader, "rect_geom");
 

source/blender/gpu/CMakeLists.txt

@@ -348,7 +348,7 @@ set(GLSL_SRC
   shaders/gpu_shader_2D_line_dashed_frag.glsl
   shaders/gpu_shader_2D_image_vert.glsl
   shaders/gpu_shader_2D_image_rect_vert.glsl
-  shaders/gpu_shader_2D_image_multi_rect_vert.glsl
+  shaders/gpu_shader_icon_multi_vert.glsl
   shaders/gpu_shader_icon_frag.glsl
   shaders/gpu_shader_icon_vert.glsl
   shaders/gpu_shader_image_frag.glsl
@@ -357,7 +357,6 @@ set(GLSL_SRC
   shaders/gpu_shader_image_overlays_stereo_merge_frag.glsl
   shaders/gpu_shader_image_shuffle_color_frag.glsl
   shaders/gpu_shader_image_color_frag.glsl
-  shaders/gpu_shader_image_varying_color_frag.glsl
   shaders/gpu_shader_3D_image_vert.glsl
   shaders/gpu_shader_3D_vert.glsl
   shaders/gpu_shader_3D_normal_vert.glsl
@@ -639,7 +638,6 @@ set(SRC_SHADER_CREATE_INFOS
   shaders/infos/gpu_shader_2D_diag_stripes_info.hh
   shaders/infos/gpu_shader_2D_image_desaturate_color_info.hh
   shaders/infos/gpu_shader_2D_image_info.hh
-  shaders/infos/gpu_shader_2D_image_multi_rect_color_info.hh
   shaders/infos/gpu_shader_2D_image_overlays_merge_info.hh
   shaders/infos/gpu_shader_2D_image_overlays_stereo_merge_info.hh
   shaders/infos/gpu_shader_2D_image_rect_color_info.hh

source/blender/gpu/GPU_shader_builtin.h

@@ -39,7 +39,7 @@ typedef enum eGPUBuiltinShader {
   /** Draw a texture with a desaturation factor. */
   GPU_SHADER_2D_IMAGE_DESATURATE_COLOR,
   /** Draw a group of texture rectangle with an associated color multiplied. */
-  GPU_SHADER_2D_IMAGE_MULTI_RECT_COLOR,
+  GPU_SHADER_ICON_MULTI,
   /** Draw a two color checker based on screen position (not UV coordinates). */
   GPU_SHADER_2D_CHECKER,
   /** Draw diagonal stripes with two alternating colors. */

source/blender/gpu/GPU_shader_shared.h

@@ -82,10 +82,10 @@ BLI_STATIC_ASSERT_ALIGN(struct SimpleLightingData, 16)
 
 #define MAX_CALLS 16
 
-struct MultiRectCallData {
+struct MultiIconCallData {
   float4 calls_data[MAX_CALLS * 3];
 };
-BLI_STATIC_ASSERT_ALIGN(struct MultiRectCallData, 16)
+BLI_STATIC_ASSERT_ALIGN(struct MultiIconCallData, 16)
 
 enum TestStatus {
   TEST_STATUS_NONE = 0,

source/blender/gpu/intern/gpu_shader_builtin.cc

@@ -42,8 +42,8 @@ static const char *builtin_shader_create_info_name(eGPUBuiltinShader shader)
       return "gpu_shader_2D_image_shuffle_color";
     case GPU_SHADER_2D_IMAGE_RECT_COLOR:
       return "gpu_shader_2D_image_rect_color";
-    case GPU_SHADER_2D_IMAGE_MULTI_RECT_COLOR:
-      return "gpu_shader_2D_image_multi_rect_color";
+    case GPU_SHADER_ICON_MULTI:
+      return "gpu_shader_icon_multi";
     case GPU_SHADER_3D_UNIFORM_COLOR:
       return "gpu_shader_3D_uniform_color";
     case GPU_SHADER_3D_FLAT_COLOR:

source/blender/gpu/metal/mtl_context.hh

@@ -768,6 +768,7 @@ class MTLContext : public Context {
   void texture_unbind_all();
   id<MTLSamplerState> get_sampler_from_state(MTLSamplerState state);
   id<MTLSamplerState> generate_sampler_from_state(MTLSamplerState state);
+  id<MTLSamplerState> generate_icon_sampler();
   id<MTLSamplerState> get_default_sampler_state();
 
   /* Metal Context pipeline state. */

source/blender/gpu/metal/mtl_context.mm

@@ -223,11 +223,13 @@ MTLContext::MTLContext(void *ghost_window, void *ghost_context)
   }
 
   /* Initialize samplers. */
-  for (uint i = 0; i < GPU_SAMPLER_MAX; i++) {
+  for (uint i = 0; i < GPU_SAMPLER_ICON; i++) {
     MTLSamplerState state;
     state.state = static_cast<eGPUSamplerState>(i);
     sampler_state_cache_[i] = this->generate_sampler_from_state(state);
   }
+  /* Special sampler for icons. */
+  sampler_state_cache_[GPU_SAMPLER_ICON] = this->generate_icon_sampler();
 }
 
 MTLContext::~MTLContext()
@@ -2024,7 +2026,6 @@ id<MTLSamplerState> MTLContext::get_sampler_from_state(MTLSamplerState sampler_s
 
 id<MTLSamplerState> MTLContext::generate_sampler_from_state(MTLSamplerState sampler_state)
 {
-  /* Check if sampler already exists for given state. */
   MTLSamplerDescriptor *descriptor = [[MTLSamplerDescriptor alloc] init];
   descriptor.normalizedCoordinates = true;
 
@@ -2067,6 +2068,21 @@ id<MTLSamplerState> MTLContext::generate_sampler_from_state(MTLSamplerState samp
   return state;
 }
 
+id<MTLSamplerState> MTLContext::generate_icon_sampler()
+{
+  MTLSamplerDescriptor *descriptor = [[MTLSamplerDescriptor alloc] init];
+  descriptor.minFilter = MTLSamplerMinMagFilterLinear;
+  descriptor.magFilter = MTLSamplerMinMagFilterLinear;
+  descriptor.mipFilter = MTLSamplerMipFilterNearest;
+  descriptor.lodMinClamp = 0;
+  descriptor.lodMaxClamp = 1;
+
+  id<MTLSamplerState> icon_state = [this->device newSamplerStateWithDescriptor:descriptor];
+  BLI_assert(icon_state != nil);
+  [descriptor autorelease];
+  return icon_state;
+}
+
 id<MTLSamplerState> MTLContext::get_default_sampler_state()
 {
   if (default_sampler_state_ == nil) {

source/blender/gpu/opengl/gl_texture.cc

@@ -594,11 +594,11 @@ void GLTexture::samplers_init()
   }
   samplers_update();
 
-  /* Custom sampler for icons. */
+  /* Custom sampler for icons.
+   * NOTE: The icon texture is sampled within the shader using a -0.5f lod bias. */
   GLuint icon_sampler = samplers_[GPU_SAMPLER_ICON];
   glSamplerParameteri(icon_sampler, GL_TEXTURE_MIN_FILTER, GL_LINEAR_MIPMAP_NEAREST);
   glSamplerParameteri(icon_sampler, GL_TEXTURE_MAG_FILTER, GL_LINEAR);
-  glSamplerParameterf(icon_sampler, GL_TEXTURE_LOD_BIAS, -0.5f);
 
   debug::object_label(GL_SAMPLER, icon_sampler, "icons");
 }

source/blender/gpu/shaders/gpu_shader_icon_frag.glsl

@@ -8,6 +8,10 @@
 
 void main()
 {
+  /* Sample texture with LOD BIAS. Used instead of custom lod bias in GPU_SAMPLER_ICON. */
+  fragColor = texture(image, texCoord_interp, -0.5) * finalColor;
+
+#ifdef DO_CORNER_MASKING
   /* Top-left rounded corner parameters. */
   const float circle_radius_outer = 0.1;
   const float circle_radius_inner = 0.075;
@@ -18,7 +22,6 @@ void main()
   const float mask_transparency = 0.25;
 
   vec2 circle_center = vec2(circle_radius_outer - text_width, 0.5);
-  fragColor = texture(image, texCoord_interp) * color;
 
   /* radius in icon space (1 is the icon width).  */
   float radius = length(mask_coord_interp - circle_center);
@@ -39,4 +42,5 @@ void main()
   }
 
   fragColor = mix(vec4(0.0), fragColor, max(mask_transparency, mask));
+#endif
 }

source/blender/gpu/shaders/gpu_shader_icon_multi_vert.glsl

@@ -5,9 +5,9 @@
 
 void main()
 {
-  vec4 rect = multi_rect_data.calls_data[gl_InstanceID * 3];
-  vec4 tex = multi_rect_data.calls_data[gl_InstanceID * 3 + 1];
-  finalColor = multi_rect_data.calls_data[gl_InstanceID * 3 + 2];
+  vec4 rect = multi_icon_data.calls_data[gl_InstanceID * 3];
+  vec4 tex = multi_icon_data.calls_data[gl_InstanceID * 3 + 1];
+  finalColor = multi_icon_data.calls_data[gl_InstanceID * 3 + 2];
 
   /* Use pos to select the right swizzle (instead of gl_VertexID)
    * in order to workaround an OSX driver bug. */

source/blender/gpu/shaders/gpu_shader_image_varying_color_frag.glsl

@@ -1,5 +0,0 @@
-
-void main()
-{
-  fragColor = texture(image, texCoord_interp) * finalColor;
-}

source/blender/gpu/shaders/infos/gpu_shader_2D_image_multi_rect_color_info.hh

@@ -1,15 +0,0 @@
-/* SPDX-License-Identifier: GPL-2.0-or-later */
-
-#include "gpu_interface_info.hh"
-#include "gpu_shader_create_info.hh"
-
-GPU_SHADER_CREATE_INFO(gpu_shader_2D_image_multi_rect_color)
-    .vertex_in(0, Type::VEC2, "pos")
-    .vertex_out(flat_color_smooth_tex_coord_interp_iface)
-    .fragment_out(0, Type::VEC4, "fragColor")
-    .uniform_buf(0, "MultiRectCallData", "multi_rect_data")
-    .sampler(0, ImageType::FLOAT_2D, "image")
-    .typedef_source("GPU_shader_shared.h")
-    .vertex_source("gpu_shader_2D_image_multi_rect_vert.glsl")
-    .fragment_source("gpu_shader_image_varying_color_frag.glsl")
-    .do_static_compilation(true);

source/blender/gpu/shaders/infos/gpu_shader_icon_info.hh

@@ -9,10 +9,11 @@
 #include "gpu_shader_create_info.hh"
 
 GPU_SHADER_CREATE_INFO(gpu_shader_icon)
+    .define("DO_CORNER_MASKING")
     .vertex_out(smooth_icon_interp_iface)
     .fragment_out(0, Type::VEC4, "fragColor")
     .push_constant(Type::MAT4, "ModelViewProjectionMatrix")
-    .push_constant(Type::VEC4, "color")
+    .push_constant(Type::VEC4, "finalColor")
     .push_constant(Type::VEC4, "rect_icon")
     .push_constant(Type::VEC4, "rect_geom")
     .push_constant(Type::FLOAT, "text_width")
@@ -20,3 +21,14 @@ GPU_SHADER_CREATE_INFO(gpu_shader_icon)
     .vertex_source("gpu_shader_icon_vert.glsl")
     .fragment_source("gpu_shader_icon_frag.glsl")
     .do_static_compilation(true);
+
+GPU_SHADER_CREATE_INFO(gpu_shader_icon_multi)
+    .vertex_in(0, Type::VEC2, "pos")
+    .vertex_out(flat_color_smooth_tex_coord_interp_iface)
+    .fragment_out(0, Type::VEC4, "fragColor")
+    .uniform_buf(0, "MultiIconCallData", "multi_icon_data")
+    .sampler(0, ImageType::FLOAT_2D, "image")
+    .typedef_source("GPU_shader_shared.h")
+    .vertex_source("gpu_shader_icon_multi_vert.glsl")
+    .fragment_source("gpu_shader_icon_frag.glsl")
+    .do_static_compilation(true);

source/blender/gpu/tests/gpu_shader_builtin_test.cc

@@ -36,7 +36,7 @@ static void test_shader_builtin()
   test_compile_builtin_shader(GPU_SHADER_3D_IMAGE_COLOR, GPU_SHADER_CFG_DEFAULT);
   test_compile_builtin_shader(GPU_SHADER_2D_IMAGE_DESATURATE_COLOR, GPU_SHADER_CFG_DEFAULT);
   test_compile_builtin_shader(GPU_SHADER_2D_IMAGE_RECT_COLOR, GPU_SHADER_CFG_DEFAULT);
-  test_compile_builtin_shader(GPU_SHADER_2D_IMAGE_MULTI_RECT_COLOR, GPU_SHADER_CFG_DEFAULT);
+  test_compile_builtin_shader(GPU_SHADER_ICON_MULTI, GPU_SHADER_CFG_DEFAULT);
   test_compile_builtin_shader(GPU_SHADER_2D_CHECKER, GPU_SHADER_CFG_DEFAULT);
   test_compile_builtin_shader(GPU_SHADER_2D_DIAG_STRIPES, GPU_SHADER_CFG_DEFAULT);
   test_compile_builtin_shader(GPU_SHADER_3D_CLIPPED_UNIFORM_COLOR, GPU_SHADER_CFG_DEFAULT);