Map renderer primitive topologies to OpenGL

docs/modernization/build-inventory.md

@@ -201,8 +201,9 @@ Known local toolchain state:
   status used by `RTT::create` and framebuffer bind/restore paths, plus RTT
   clear color/depth masks and color-write-mask query tokens. `RTT` no longer
   spells GL enum names directly. It also
-  validates Shape index-type, fill/stroke primitive-mode, buffer target, static
+  validates renderer API primitive-topology to OpenGL draw-mode mapping, Shape
-  upload usage, and vertex attribute component/normalization mapping used by
+  index-type, fill/stroke primitive-mode, buffer target, static upload usage,
+  and vertex attribute component/normalization mapping used by
   the legacy mesh draw path, plus the PanoPainter cube-face to OpenGL
   texture-target mapping used by `TextureCube`.
   It also owns and validates sampler wrap S/T/R, min/mag filter, and desktop

docs/modernization/roadmap.md

@@ -455,10 +455,10 @@ framebuffer targets, binding queries, attachment points, and completion status
 used by `RTT::create` and framebuffer bind/restore paths, also live in
 `pp_renderer_gl`. RTT clear color/depth masks and color-write-mask query tokens
 also live in `pp_renderer_gl`. `RTT` no longer spells GL enum names directly.
-Mesh index-type and primitive-mode
+Renderer API primitive-topology to OpenGL draw-mode mapping, mesh index-type
-decisions used by legacy `Shape` drawing, plus Shape buffer targets, static
+and primitive-mode decisions used by legacy `Shape` drawing, plus Shape buffer
-upload usage, and vertex attribute component/normalization tokens, also live
+targets, static upload usage, and vertex attribute component/normalization
-in `pp_renderer_gl`. The PanoPainter cube-face to
+tokens, also live in `pp_renderer_gl`. The PanoPainter cube-face to
 OpenGL texture-target mapping used by `TextureCube` also lives in
 `pp_renderer_gl`. The legacy app delegates extension, upload-format,
 framebuffer diagnostic, framebuffer blit, render-target setup, clear-state,

src/renderer_gl/opengl_capabilities.cpp

@@ -22,6 +22,7 @@ constexpr std::uint32_t gl_false = 0U;
 constexpr std::uint32_t gl_points = 0x0000U;
 constexpr std::uint32_t gl_lines = 0x0001U;
 constexpr std::uint32_t gl_triangles = 0x0004U;
+constexpr std::uint32_t gl_triangle_strip = 0x0005U;
 constexpr std::uint32_t gl_fragment_shader = 0x8B30U;
 constexpr std::uint32_t gl_vertex_shader = 0x8B31U;
 constexpr std::uint32_t gl_compile_status = 0x8B81U;
@@ -459,6 +460,20 @@ std::uint32_t framebuffer_blit_filter(bool linear) noexcept
     return linear ? gl_linear : gl_nearest;
 }
 
+std::uint32_t primitive_mode_for_renderer_topology(pp::renderer::PrimitiveTopology topology) noexcept
+{
+    switch (topology) {
+    case pp::renderer::PrimitiveTopology::triangles:
+        return gl_triangles;
+    case pp::renderer::PrimitiveTopology::triangle_strip:
+        return gl_triangle_strip;
+    case pp::renderer::PrimitiveTopology::lines:
+        return gl_lines;
+    default:
+        return 0U;
+    }
+}
+
 std::uint32_t index_type_for_index_size(std::uint32_t index_size_bytes) noexcept
 {
     switch (index_size_bytes) {

src/renderer_gl/opengl_capabilities.h

@@ -95,6 +95,8 @@ struct OpenGlWindowsWglContextConfig {
 [[nodiscard]] std::uint32_t framebuffer_depth_buffer_mask() noexcept;
 [[nodiscard]] std::uint32_t color_write_mask_query() noexcept;
 [[nodiscard]] std::uint32_t framebuffer_blit_filter(bool linear) noexcept;
+[[nodiscard]] std::uint32_t primitive_mode_for_renderer_topology(
+    pp::renderer::PrimitiveTopology topology) noexcept;
 [[nodiscard]] std::uint32_t index_type_for_index_size(std::uint32_t index_size_bytes) noexcept;
 [[nodiscard]] std::uint32_t primitive_mode_for_fill_count(std::uint32_t vertex_or_index_count) noexcept;
 [[nodiscard]] std::uint32_t primitive_mode_for_stroke_count(std::uint32_t vertex_or_index_count) noexcept;

tests/renderer_gl/capabilities_tests.cpp

@@ -258,6 +258,22 @@ void maps_framebuffer_blit_parameters(pp::tests::Harness& h)
     PP_EXPECT(h, pp::renderer::gl::framebuffer_blit_filter(false) == 0x2600U);
 }
 
+void maps_renderer_primitive_topologies_to_draw_modes(pp::tests::Harness& h)
+{
+    PP_EXPECT(h, pp::renderer::gl::primitive_mode_for_renderer_topology(
+                     pp::renderer::PrimitiveTopology::triangles)
+                     == 0x0004U);
+    PP_EXPECT(h, pp::renderer::gl::primitive_mode_for_renderer_topology(
+                     pp::renderer::PrimitiveTopology::triangle_strip)
+                     == 0x0005U);
+    PP_EXPECT(h, pp::renderer::gl::primitive_mode_for_renderer_topology(
+                     pp::renderer::PrimitiveTopology::lines)
+                     == 0x0001U);
+    PP_EXPECT(h, pp::renderer::gl::primitive_mode_for_renderer_topology(
+                     static_cast<pp::renderer::PrimitiveTopology>(255U))
+                     == 0U);
+}
+
 void maps_shape_index_and_primitive_modes(pp::tests::Harness& h)
 {
     constexpr std::uint32_t gl_points = 0x0000U;
@@ -545,6 +561,7 @@ int main()
     harness.run("names_framebuffer_status_codes", names_framebuffer_status_codes);
     harness.run("maps_framebuffer_render_target_parameters", maps_framebuffer_render_target_parameters);
     harness.run("maps_framebuffer_blit_parameters", maps_framebuffer_blit_parameters);
+    harness.run("maps_renderer_primitive_topologies_to_draw_modes", maps_renderer_primitive_topologies_to_draw_modes);
     harness.run("maps_shape_index_and_primitive_modes", maps_shape_index_and_primitive_modes);
     harness.run("maps_panopainter_cube_faces_to_texture_targets", maps_panopainter_cube_faces_to_texture_targets);
     harness.run("exposes_default_render_target_texture_parameters", exposes_default_render_target_texture_parameters);