Add support for scissor

src/engine/renderer/opengl/renderer_opengl.cc

@@ -58,6 +58,17 @@ int RendererOpenGL::GetScreenHeight() const {
   return screen_height_;
 }
 
+void RendererOpenGL::SetScissor(int x, int y, int width, int height) {
+  DCHECK(x >= 0 && y >= 0 && width >= 0 && height >= 0);
+  DCHECK(x + width <= GetScreenWidth() && y + height <= GetScreenHeight());
+  glScissor(x, screen_height_ - y - height, width, height);
+  glEnable(GL_SCISSOR_TEST);
+}
+
+void RendererOpenGL::ResetScissor() {
+  glDisable(GL_SCISSOR_TEST);
+}
+
 uint64_t RendererOpenGL::CreateGeometry(std::unique_ptr<Mesh> mesh) {
   // Verify that we have a valid layout and get the total byte size per vertex.
   GLuint vertex_size = mesh->GetVertexSize();
@@ -417,6 +428,10 @@ void RendererOpenGL::SetUniform(uint64_t resource_id,
     glUniform1i(index, val);
 }
 
+void RendererOpenGL::PrepareForDrawing() {
+  glDisable(GL_SCISSOR_TEST);
+}
+
 void RendererOpenGL::ContextLost() {
   LOG(0) << "Context lost.";
 

src/engine/renderer/opengl/renderer_opengl.h

@@ -31,6 +31,9 @@ class RendererOpenGL final : public Renderer {
   int GetScreenWidth() const final;
   int GetScreenHeight() const final;
 
+  void SetScissor(int x, int y, int width, int height) final;
+  void ResetScissor() final;
+
   uint64_t CreateGeometry(std::unique_ptr<Mesh> mesh) final;
   void DestroyGeometry(uint64_t resource_id) final;
   void Draw(uint64_t resource_id,
@@ -67,7 +70,7 @@ class RendererOpenGL final : public Renderer {
   void SetUniform(uint64_t resource_id, const std::string& name, int val) final;
   void UploadUniforms(uint64_t resource_id) final {}
 
-  void PrepareForDrawing() final {}
+  void PrepareForDrawing() final;
   void Present() final;
 
   size_t GetAndResetFPS() final;

src/engine/renderer/renderer.h

@@ -38,6 +38,9 @@ class Renderer {
   virtual int GetScreenWidth() const = 0;
   virtual int GetScreenHeight() const = 0;
 
+  virtual void SetScissor(int x, int y, int width, int height) = 0;
+  virtual void ResetScissor() = 0;
+
   virtual uint64_t CreateGeometry(std::unique_ptr<Mesh> mesh) = 0;
   virtual void DestroyGeometry(uint64_t resource_id) = 0;
   virtual void Draw(uint64_t resource_id,

src/engine/renderer/vulkan/renderer_vulkan.cc

@@ -390,6 +390,27 @@ int RendererVulkan::GetScreenHeight() const {
   return context_.GetWindowHeight();
 }
 
+void RendererVulkan::SetScissor(int x, int y, int width, int height) {
+  DCHECK(x >= 0 && y >= 0 && width >= 0 && height >= 0);
+  DCHECK(x + width <= GetScreenWidth() && y + height <= GetScreenHeight());
+
+  VkRect2D scissor;
+  scissor.offset.x = x;
+  scissor.offset.y = y;
+  scissor.extent.width = width;
+  scissor.extent.height = height;
+  vkCmdSetScissor(frames_[current_frame_].draw_command_buffer, 0, 1, &scissor);
+}
+
+void RendererVulkan::ResetScissor() {
+  VkRect2D scissor;
+  scissor.offset.x = 0;
+  scissor.offset.y = 0;
+  scissor.extent.width = context_.GetWindowWidth();
+  scissor.extent.height = context_.GetWindowHeight();
+  vkCmdSetScissor(frames_[current_frame_].draw_command_buffer, 0, 1, &scissor);
+}
+
 uint64_t RendererVulkan::CreateGeometry(std::unique_ptr<Mesh> mesh) {
   auto& geometry = geometries_[++last_resource_id_] = {};
 

src/engine/renderer/vulkan/renderer_vulkan.h

@@ -33,6 +33,9 @@ class RendererVulkan final : public Renderer {
   int GetScreenWidth() const final;
   int GetScreenHeight() const final;
 
+  void SetScissor(int x, int y, int width, int height) final;
+  void ResetScissor() final;
+
   uint64_t CreateGeometry(std::unique_ptr<Mesh> mesh) final;
   void DestroyGeometry(uint64_t resource_id) final;
   void Draw(uint64_t resource_id,