Add stroke composite feedback planner

src/paint_renderer/compositor.cpp

@@ -6,6 +6,40 @@ namespace pp::paint_renderer {
 
 namespace {
 
+[[nodiscard]] bool is_valid_blend_mode(pp::paint::BlendMode mode) noexcept
+{
+    switch (mode) {
+    case pp::paint::BlendMode::normal:
+    case pp::paint::BlendMode::multiply:
+    case pp::paint::BlendMode::screen:
+    case pp::paint::BlendMode::color_dodge:
+    case pp::paint::BlendMode::overlay:
+        return true;
+    }
+
+    return false;
+}
+
+[[nodiscard]] bool is_valid_stroke_blend_mode(pp::paint::StrokeBlendMode mode) noexcept
+{
+    switch (mode) {
+    case pp::paint::StrokeBlendMode::normal:
+    case pp::paint::StrokeBlendMode::multiply:
+    case pp::paint::StrokeBlendMode::subtract:
+    case pp::paint::StrokeBlendMode::darken:
+    case pp::paint::StrokeBlendMode::overlay:
+    case pp::paint::StrokeBlendMode::color_dodge:
+    case pp::paint::StrokeBlendMode::color_burn:
+    case pp::paint::StrokeBlendMode::linear_burn:
+    case pp::paint::StrokeBlendMode::hard_mix:
+    case pp::paint::StrokeBlendMode::linear_height:
+    case pp::paint::StrokeBlendMode::height:
+        return true;
+    }
+
+    return false;
+}
+
 [[nodiscard]] pp::foundation::Result<std::size_t> expected_pixel_count(pp::renderer::Extent2D extent) noexcept
 {
     const auto extent_status = pp::renderer::validate_extent(extent);
@@ -29,6 +63,20 @@ namespace {
     return pp::foundation::Result<std::size_t>::success(static_cast<std::size_t>(count));
 }
 
+[[nodiscard]] StrokeCompositePath composite_path_from_feedback(pp::renderer::PaintFeedbackPath path) noexcept
+{
+    switch (path) {
+    case pp::renderer::PaintFeedbackPath::none:
+        return StrokeCompositePath::fixed_function_blend;
+    case pp::renderer::PaintFeedbackPath::framebuffer_fetch:
+        return StrokeCompositePath::framebuffer_fetch;
+    case pp::renderer::PaintFeedbackPath::ping_pong_textures:
+        return StrokeCompositePath::ping_pong_textures;
+    }
+
+    return StrokeCompositePath::fixed_function_blend;
+}
+
 }
 
 pp::foundation::Status composite_layer(
@@ -62,4 +110,78 @@ pp::foundation::Status composite_layer(
     return pp::foundation::Status::success();
 }
 
+bool stroke_composite_requires_feedback(
+    pp::paint::BlendMode layer_blend_mode,
+    pp::paint::StrokeBlendMode stroke_blend_mode,
+    bool dual_brush_blend,
+    bool pattern_blend) noexcept
+{
+    return layer_blend_mode != pp::paint::BlendMode::normal
+        || stroke_blend_mode != pp::paint::StrokeBlendMode::normal
+        || dual_brush_blend
+        || pattern_blend;
+}
+
+pp::foundation::Result<StrokeCompositePlan> plan_stroke_composite(
+    pp::renderer::RenderDeviceFeatures features,
+    StrokeCompositeRequest request) noexcept
+{
+    if (!is_valid_blend_mode(request.layer_blend_mode)) {
+        return pp::foundation::Result<StrokeCompositePlan>::failure(
+            pp::foundation::Status::invalid_argument("unknown layer blend mode"));
+    }
+
+    if (!is_valid_stroke_blend_mode(request.stroke_blend_mode)) {
+        return pp::foundation::Result<StrokeCompositePlan>::failure(
+            pp::foundation::Status::invalid_argument("unknown stroke blend mode"));
+    }
+
+    const pp::renderer::TextureDesc target_desc {
+        .extent = request.extent,
+        .format = request.target_format,
+        .usage = request.target_usage,
+        .debug_name = "stroke-composite-target",
+    };
+    const auto complex_blend = stroke_composite_requires_feedback(
+        request.layer_blend_mode,
+        request.stroke_blend_mode,
+        request.dual_brush_blend,
+        request.pattern_blend);
+    const auto feedback = pp::renderer::plan_paint_feedback(features, target_desc, complex_blend);
+    if (!feedback) {
+        return pp::foundation::Result<StrokeCompositePlan>::failure(feedback.status());
+    }
+
+    StrokeCompositePlan plan;
+    plan.path = composite_path_from_feedback(feedback.value().path);
+    plan.feedback = feedback.value();
+    plan.target_desc = target_desc;
+    plan.target_bytes = feedback.value().target_bytes;
+    plan.auxiliary_bytes = feedback.value().requires_auxiliary_texture
+        ? feedback.value().target_bytes
+        : 0U;
+    plan.estimated_working_bytes = plan.target_bytes + plan.auxiliary_bytes;
+    plan.complex_blend = complex_blend;
+    plan.reads_destination_color = feedback.value().reads_destination_color;
+    plan.requires_auxiliary_texture = feedback.value().requires_auxiliary_texture;
+    plan.requires_texture_copy = feedback.value().requires_texture_copy;
+    plan.requires_render_target_blit = feedback.value().requires_render_target_blit;
+    plan.requires_explicit_transition = feedback.value().requires_explicit_transition;
+    return pp::foundation::Result<StrokeCompositePlan>::success(plan);
+}
+
+const char* stroke_composite_path_name(StrokeCompositePath path) noexcept
+{
+    switch (path) {
+    case StrokeCompositePath::fixed_function_blend:
+        return "fixed_function_blend";
+    case StrokeCompositePath::framebuffer_fetch:
+        return "framebuffer_fetch";
+    case StrokeCompositePath::ping_pong_textures:
+        return "ping_pong_textures";
+    }
+
+    return "unknown";
+}
+
 }