Narrow retained canvas stroke execution helpers

src/legacy_canvas_stroke_commit_services.h

@@ -4,6 +4,7 @@
 
 #include <algorithm>
 #include <array>
+#include <cstdint>
 #include <functional>
 #include <string_view>
 
@@ -46,12 +47,100 @@ struct LegacyCanvasStrokeCommitResult {
     int committed_faces = 0;
 };
 
+struct LegacyCanvasStrokeCommitCopyExtent {
+    int width = 0;
+    int height = 0;
+};
+
 [[nodiscard]] inline std::size_t legacy_canvas_stroke_commit_step_count(
     const pp::paint_renderer::CanvasStrokeCommitSequencePlan& sequence) noexcept
 {
     return std::min(sequence.step_count, sequence.steps.size());
 }
 
+[[nodiscard]] inline std::size_t legacy_canvas_stroke_commit_texture_binding_count(
+    const pp::paint_renderer::CanvasStrokeCommitSequencePlan& sequence) noexcept
+{
+    return std::min(sequence.texture_binding_count, sequence.texture_bindings.size());
+}
+
+[[nodiscard]] inline int legacy_canvas_stroke_commit_texture_slot(
+    const pp::paint_renderer::CanvasStrokeCommitSequencePlan& sequence,
+    pp::paint_renderer::CanvasStrokeCommitTextureRole role) noexcept
+{
+    const auto binding_count = legacy_canvas_stroke_commit_texture_binding_count(sequence);
+    for (std::size_t binding_index = 0; binding_index < binding_count; ++binding_index) {
+        const auto& binding = sequence.texture_bindings[binding_index];
+        if (binding.role == role) {
+            return static_cast<int>(binding.slot);
+        }
+    }
+
+    return -1;
+}
+
+template <typename SetActiveTextureUnit, typename BindTextureRole, typename BindSamplerRole>
+inline void bind_legacy_canvas_stroke_commit_inputs(
+    const pp::paint_renderer::CanvasStrokeCommitSequencePlan& sequence,
+    SetActiveTextureUnit&& set_active_texture_unit,
+    BindTextureRole&& bind_texture_role,
+    BindSamplerRole&& bind_sampler_role)
+{
+    const auto binding_count = legacy_canvas_stroke_commit_texture_binding_count(sequence);
+    for (std::size_t binding_index = 0; binding_index < binding_count; ++binding_index) {
+        const auto& binding = sequence.texture_bindings[binding_index];
+        set_active_texture_unit(static_cast<int>(binding.slot));
+        bind_texture_role(binding.role);
+        bind_sampler_role(binding.role, static_cast<int>(binding.slot));
+    }
+}
+
+template <typename SetupShader, typename DrawPlane>
+inline void execute_legacy_canvas_stroke_commit_erase(
+    SetupShader&& setup_shader,
+    DrawPlane&& draw_plane)
+{
+    setup_shader();
+    draw_plane();
+}
+
+template <typename SetupShader, typename DrawPlane>
+inline void execute_legacy_canvas_stroke_commit_paint(
+    SetupShader&& setup_shader,
+    DrawPlane&& draw_plane)
+{
+    setup_shader();
+    draw_plane();
+}
+
+template <typename SetupShader, typename SetActiveTextureUnit, typename BindLayerScratch, typename CopyFramebufferToTexture>
+inline void copy_legacy_canvas_stroke_commit_to_dilate_source(
+    const pp::paint_renderer::CanvasStrokeCommitSequencePlan& sequence,
+    SetupShader&& setup_shader,
+    SetActiveTextureUnit&& set_active_texture_unit,
+    BindLayerScratch&& bind_layer_scratch,
+    CopyFramebufferToTexture&& copy_framebuffer_to_texture,
+    LegacyCanvasStrokeCommitCopyExtent extent)
+{
+    const auto layer_scratch_slot = legacy_canvas_stroke_commit_texture_slot(
+        sequence,
+        pp::paint_renderer::CanvasStrokeCommitTextureRole::layer_scratch);
+    if (layer_scratch_slot < 0 || extent.width <= 0 || extent.height <= 0) {
+        return;
+    }
+
+    setup_shader();
+    set_active_texture_unit(layer_scratch_slot);
+    bind_layer_scratch();
+    copy_framebuffer_to_texture(0, 0, 0, 0, extent.width, extent.height);
+}
+
+template <typename DrawPlane>
+inline void execute_legacy_canvas_stroke_commit_dilate(DrawPlane&& draw_plane)
+{
+    draw_plane();
+}
+
 [[nodiscard]] inline bool legacy_canvas_stroke_commit_callbacks_ready(
     const LegacyCanvasStrokeCommitCallbacks& callbacks) noexcept
 {