From 5cd49386989d8b01e7c2033e19221b384e1564e7 Mon Sep 17 00:00:00 2001
From: Krzysztof Jakubowski <nadult@fastmail.fm>
Date: Wed, 8 Jan 2025 20:34:06 +0100
Subject: [PATCH] Canvas2D: added scissor rect support

---
 include/fwk/gfx/canvas_2d.h | 10 ++++++++--
 include/fwk/gfx/drawing.h   |  4 ++--
 src/gfx/canvas_2d.cpp       | 21 ++++++++++++++++++++-
 src/gfx/drawing.cpp         | 12 +++++++++++-
 4 files changed, 41 insertions(+), 6 deletions(-)

diff --git a/include/fwk/gfx/canvas_2d.h b/include/fwk/gfx/canvas_2d.h
index 2b686baf..3a3abdce 100644
--- a/include/fwk/gfx/canvas_2d.h
+++ b/include/fwk/gfx/canvas_2d.h
@@ -39,6 +39,9 @@ class Canvas2D {
 	void setMaterial(const SimpleMaterial &);
 	SimpleMaterial getMaterial() const;
 
+	void setScissorRect(Maybe<IRect>);
+	Maybe<IRect> getScissorRect() const;
+
 	void pushViewMatrix();
 	void popViewMatrix();
 	void mulViewMatrix(const Matrix4 &);
@@ -79,12 +82,14 @@ class Canvas2D {
 
   private:
 	struct Group {
-		Group(int first_index, int pipeline_index)
-			: first_index(first_index), num_indices(0), pipeline_index(pipeline_index) {}
+		Group(int first_index, int pipeline_index, int scissor_rect_index)
+			: first_index(first_index), num_indices(0), pipeline_index(pipeline_index),
+			  scissor_rect_index(scissor_rect_index) {}
 
 		PVImageView texture;
 		int first_index, num_indices;
 		int pipeline_index;
+		int scissor_rect_index;
 	};
 
 	int getPipeline(const SimplePipelineSetup &);
@@ -99,6 +104,7 @@ class Canvas2D {
 	vector<SimplePipelineSetup> m_pipelines;
 	vector<Matrix4> m_group_matrices;
 	vector<Group> m_groups;
+	vector<IRect> m_scissor_rects;
 
 	PodVector<float3> m_positions;
 	PodVector<TexCoord> m_tex_coords;
diff --git a/include/fwk/gfx/drawing.h b/include/fwk/gfx/drawing.h
index 578d3bef..7c7fc762 100644
--- a/include/fwk/gfx/drawing.h
+++ b/include/fwk/gfx/drawing.h
@@ -61,20 +61,20 @@ struct SimpleDrawCall {
 
 	// Vertex data:
 	// indices, tex_coords, normals & colors are optional
-
 	VBufferSpan<u32> indices;
 	VBufferSpan<float3> vertices;
 	VBufferSpan<float2> tex_coords;
 	VBufferSpan<IColor> colors;
 
 	// Instance data:
-
 	struct Instance {
 		PVImageView texture;
 		int pipeline_index;
 		int first_index, num_vertices;
+		int scissor_rect_index;
 	};
 	VBufferSpan<Matrix4> instance_matrices;
+	vector<IRect> scissor_rects;
 	vector<Instance> instances;
 	vector<PVPipeline> pipelines;
 };
diff --git a/src/gfx/canvas_2d.cpp b/src/gfx/canvas_2d.cpp
index d2455014..b95b33f1 100644
--- a/src/gfx/canvas_2d.cpp
+++ b/src/gfx/canvas_2d.cpp
@@ -27,7 +27,7 @@ namespace fwk {
 Canvas2D::Canvas2D(const IRect &viewport, Orient2D orient)
 	: m_matrix_stack(projectionMatrix2D(viewport, orient), viewMatrix2D(viewport, float2(0, 0))),
 	  m_viewport(viewport) {
-	m_groups.emplace_back(0, getPipeline({}));
+	m_groups.emplace_back(0, getPipeline({}), -1);
 	m_group_matrices.emplace_back(m_matrix_stack.fullMatrix());
 }
 
@@ -81,10 +81,12 @@ Ex<SimpleDrawCall> Canvas2D::genDrawCall(ShaderCompiler &compiler, VulkanDevice
 		instance.pipeline_index = group.pipeline_index + (skip_first_pipeline ? -1 : 0);
 		instance.num_vertices = group.num_indices;
 		instance.first_index = group.first_index;
+		instance.scissor_rect_index = group.scissor_rect_index;
 	}
 
 	auto setups = subSpan(m_pipelines, skip_first_pipeline ? 1 : 0);
 	dc.pipelines = EX_PASS(SimpleDrawCall::makePipelines(compiler, device, render_pass, setups));
+	dc.scissor_rects = m_scissor_rects;
 	return dc;
 }
 
@@ -160,6 +162,23 @@ SimpleMaterial Canvas2D::getMaterial() const {
 	return SimpleMaterial{group.texture, IColor(m_cur_color), pipe.flags, pipe.blending_mode};
 }
 
+void Canvas2D::setScissorRect(Maybe<IRect> rect) {
+	if(getScissorRect() == rect)
+		return;
+	splitGroup();
+	int scissor_index = -1;
+	if(rect) {
+		scissor_index = m_scissor_rects.size();
+		m_scissor_rects.emplace_back(*rect);
+	}
+	m_groups.back().scissor_rect_index = scissor_index;
+}
+
+Maybe<IRect> Canvas2D::getScissorRect() const {
+	int index = m_groups.back().scissor_rect_index;
+	return index == -1 ? Maybe<IRect>() : m_scissor_rects[index];
+}
+
 void Canvas2D::pushViewMatrix() {
 	m_matrix_stack.pushViewMatrix();
 	if(!splitGroup())
diff --git a/src/gfx/drawing.cpp b/src/gfx/drawing.cpp
index 4ceac2c6..f47dcba6 100644
--- a/src/gfx/drawing.cpp
+++ b/src/gfx/drawing.cpp
@@ -127,7 +127,9 @@ void SimpleDrawCall::render(VulkanDevice &device) {
 		cmds.bindIndices(indices);
 
 	uint instance_id = 0;
-	for(auto &instance : instances) {
+	for(int i = 0; i < instances.size(); i++) {
+		auto &instance = instances[i];
+
 		if(instance.pipeline_index != prev_pipeline_idx) {
 			cmds.bind(pipelines[instance.pipeline_index]);
 			prev_pipeline_idx = instance.pipeline_index;
@@ -137,12 +139,20 @@ void SimpleDrawCall::render(VulkanDevice &device) {
 			cmds.bindDS(1).set(0, {{sampler, instance.texture}});
 			prev_tex = instance.texture;
 		}
+		if(i == 0 || instance.scissor_rect_index != instances[i - 1].scissor_rect_index) {
+			Maybe<IRect> scissor_rect;
+			if(instance.scissor_rect_index != -1)
+				scissor_rect = scissor_rects[instance.scissor_rect_index];
+			cmds.setScissor(scissor_rect);
+		}
 
 		if(indices)
 			cmds.drawIndexed(instance.num_vertices, 1, instance.first_index, instance_id++);
 		else
 			cmds.draw(instance.num_vertices, 1, instance.first_index, instance_id++);
 	}
+
+	cmds.setScissor(none);
 }
 
 /*