Map renderer color write masks to OpenGL

docs/modernization/build-inventory.md

@@ -215,8 +215,9 @@ Known local toolchain state:
   queries, active-uniform count query, and matrix-uniform transpose token used
   by legacy `Shader` creation also live here. Renderer API blend factor/op to
   OpenGL token mapping is tested here with explicit support flags so `GL_ZERO`
-  stays distinguishable from unsupported enum values. Renderer API depth
+  stays distinguishable from unsupported enum values. Renderer API blend-state
-  compare-op to OpenGL depth-function mapping is tested here too. `Shader` no longer spells GL enum
+  color-write masks and depth compare-op to OpenGL depth-function mapping are
+  tested here too. `Shader` no longer spells GL enum
   names directly. It also owns the PanoPainter shader uniform catalog and legacy hash
   mapping used by `Shader` active-uniform discovery and the uniform uniqueness
   check. App OpenGL initialization debug severity, debug output, GL info string,

docs/modernization/roadmap.md

@@ -473,8 +473,8 @@ count query, and matrix-uniform transpose token also live in `pp_renderer_gl`
 and are consumed by legacy `Shader` creation. Renderer API blend factor/op to
 OpenGL token mapping also lives in `pp_renderer_gl`, with explicit support flags
 so `GL_ZERO` remains distinguishable from unsupported enum values. Renderer API
-depth compare-op to OpenGL depth-function mapping also lives in
+blend-state color-write masks and depth compare-op to OpenGL depth-function
-`pp_renderer_gl`. Shader uniform hashing, catalog
+mapping also live in `pp_renderer_gl`. Shader uniform hashing, catalog
 validation, active-uniform mapping, and the legacy uniform uniqueness check now
 delegate to `pp_renderer_gl` as well. `Shader` no longer spells GL enum names
 directly. App OpenGL initialization debug severity, debug output, GL info

src/renderer_gl/opengl_capabilities.cpp

@@ -803,6 +803,16 @@ std::uint8_t color_write_enabled() noexcept
     return gl_boolean_true;
 }
 
+OpenGlColorWriteMask color_write_mask_for_renderer_blend_state(pp::renderer::BlendState state) noexcept
+{
+    return OpenGlColorWriteMask {
+        .r = state.write_r ? gl_boolean_true : gl_boolean_false,
+        .g = state.write_g ? gl_boolean_true : gl_boolean_false,
+        .b = state.write_b ? gl_boolean_true : gl_boolean_false,
+        .a = state.write_a ? gl_boolean_true : gl_boolean_false,
+    };
+}
+
 std::uint32_t linear_texture_filter() noexcept
 {
     return gl_linear;

src/renderer_gl/opengl_capabilities.h

@@ -39,6 +39,13 @@ struct OpenGlEnumMapping {
     bool supported = false;
 };
 
+struct OpenGlColorWriteMask {
+    std::uint8_t r = 0;
+    std::uint8_t g = 0;
+    std::uint8_t b = 0;
+    std::uint8_t a = 0;
+};
+
 struct OpenGlReadbackFormat {
     std::uint32_t pixel_format = 0;
     std::uint32_t component_type = 0;
@@ -155,6 +162,8 @@ struct OpenGlWindowsWglContextConfig {
 [[nodiscard]] std::uint32_t rgba32f_internal_format() noexcept;
 [[nodiscard]] std::uint8_t color_write_disabled() noexcept;
 [[nodiscard]] std::uint8_t color_write_enabled() noexcept;
+[[nodiscard]] OpenGlColorWriteMask color_write_mask_for_renderer_blend_state(
+    pp::renderer::BlendState state) noexcept;
 [[nodiscard]] std::uint32_t linear_texture_filter() noexcept;
 [[nodiscard]] std::uint32_t linear_mipmap_linear_texture_filter() noexcept;
 [[nodiscard]] std::uint32_t nearest_texture_filter() noexcept;

tests/renderer_gl/capabilities_tests.cpp

@@ -535,6 +535,29 @@ void maps_renderer_blend_state_tokens(pp::tests::Harness& h)
     PP_EXPECT(h, invalid_op.value == 0U);
 }
 
+void maps_renderer_color_write_masks(pp::tests::Harness& h)
+{
+    const auto default_mask = pp::renderer::gl::color_write_mask_for_renderer_blend_state(
+        pp::renderer::BlendState {});
+    const auto mixed_mask = pp::renderer::gl::color_write_mask_for_renderer_blend_state(
+        pp::renderer::BlendState { .write_r = true, .write_g = false, .write_b = true, .write_a = false });
+    const auto disabled_mask = pp::renderer::gl::color_write_mask_for_renderer_blend_state(
+        pp::renderer::BlendState { .write_r = false, .write_g = false, .write_b = false, .write_a = false });
+
+    PP_EXPECT(h, default_mask.r == 1U);
+    PP_EXPECT(h, default_mask.g == 1U);
+    PP_EXPECT(h, default_mask.b == 1U);
+    PP_EXPECT(h, default_mask.a == 1U);
+    PP_EXPECT(h, mixed_mask.r == 1U);
+    PP_EXPECT(h, mixed_mask.g == 0U);
+    PP_EXPECT(h, mixed_mask.b == 1U);
+    PP_EXPECT(h, mixed_mask.a == 0U);
+    PP_EXPECT(h, disabled_mask.r == 0U);
+    PP_EXPECT(h, disabled_mask.g == 0U);
+    PP_EXPECT(h, disabled_mask.b == 0U);
+    PP_EXPECT(h, disabled_mask.a == 0U);
+}
+
 void maps_renderer_depth_compare_tokens(pp::tests::Harness& h)
 {
     const auto never = pp::renderer::gl::compare_function_for_renderer_compare_op(
@@ -706,6 +729,7 @@ int main()
     harness.run("exposes_shader_attribute_binding_catalog", exposes_shader_attribute_binding_catalog);
     harness.run("maps_app_initialization_parameters", maps_app_initialization_parameters);
     harness.run("maps_renderer_blend_state_tokens", maps_renderer_blend_state_tokens);
+    harness.run("maps_renderer_color_write_masks", maps_renderer_color_write_masks);
     harness.run("maps_renderer_depth_compare_tokens", maps_renderer_depth_compare_tokens);
     harness.run("maps_windows_wgl_core_context_parameters", maps_windows_wgl_core_context_parameters);
     harness.run("rejects_invalid_shader_attribute_binding_catalogs", rejects_invalid_shader_attribute_binding_catalogs);