From e40393fec46a18cdfb7eb32c2eef9f143707397e Mon Sep 17 00:00:00 2001
From: Connor McLaughlin <mclaughc@outlook.com>
Date: Sat, 14 Sep 2019 21:54:58 +1000
Subject: [PATCH] GPU: Use scissor test for drawing area

---
 src/pse/gpu_hw.cpp        | 10 ++--------
 src/pse/gpu_hw_opengl.cpp | 21 +++++++++++++++++++--
 2 files changed, 21 insertions(+), 10 deletions(-)

diff --git a/src/pse/gpu_hw.cpp b/src/pse/gpu_hw.cpp
index e89d50210..a1599df6a 100644
--- a/src/pse/gpu_hw.cpp
+++ b/src/pse/gpu_hw.cpp
@@ -31,12 +31,6 @@ void GPU_HW::LoadVertices(RenderCommand rc, u32 num_vertices)
         hw_vert.x = vp.x();
         hw_vert.y = vp.y();
 
-        // excluding lower-right coordinates
-        if ((i & UINT32_C(1)) != 0)
-          hw_vert.x--;
-        if ((i & UINT32_C(2)) != 0)
-          hw_vert.y--;
-
         if (textured)
           hw_vert.texcoord = Truncate16(m_GP0_command[buffer_pos++]);
         else
@@ -113,9 +107,9 @@ void GPU_HW::CalcViewport(int* x, int* y, int* width, int* height)
 void GPU_HW::CalcScissorRect(int* left, int* top, int* right, int* bottom)
 {
   *left = m_drawing_area.top_left_x;
-  *right = m_drawing_area.bottom_right_x;
+  *right = m_drawing_area.bottom_right_x + 1;
   *top = m_drawing_area.top_left_y;
-  *bottom = m_drawing_area.bottom_right_y;
+  *bottom = m_drawing_area.bottom_right_y + 1;
 }
 
 static void DefineMacro(std::stringstream& ss, const char* name, bool enabled)
diff --git a/src/pse/gpu_hw_opengl.cpp b/src/pse/gpu_hw_opengl.cpp
index a8a91ae22..ea4c1d206 100644
--- a/src/pse/gpu_hw_opengl.cpp
+++ b/src/pse/gpu_hw_opengl.cpp
@@ -175,7 +175,19 @@ void GPU_HW_OpenGL::SetViewport()
   glViewport(x, y, width, height);
 }
 
-void GPU_HW_OpenGL::SetScissor() {}
+void GPU_HW_OpenGL::SetScissor()
+{
+  int left, top, right, bottom;
+  CalcScissorRect(&left, &top, &right, &bottom);
+
+  const int width = right - left;
+  const int height = bottom - top;
+  const int x = left;
+  const int y = VRAM_HEIGHT - bottom;
+
+  Log_DebugPrintf("SetScissor: (%d-%d, %d-%d)", x, x + width, y, y + height);
+  glScissor(x, y, width, height);
+}
 
 inline u32 ConvertRGBA5551ToRGBA8888(u16 color)
 {
@@ -252,7 +264,6 @@ void GPU_HW_OpenGL::FillVRAM(u32 x, u32 y, u32 width, u32 height, u32 color)
   const auto [r, g, b, a] = RGBA8ToFloat(color);
   glClearColor(r, g, b, a);
   glClear(GL_COLOR_BUFFER_BIT);
-  glDisable(GL_SCISSOR_TEST);
 }
 
 void GPU_HW_OpenGL::UpdateVRAM(u32 x, u32 y, u32 width, u32 height, const void* data)
@@ -293,6 +304,7 @@ void GPU_HW_OpenGL::UpdateTexturePageTexture()
   m_framebuffer_texture->Bind();
 
   glDisable(GL_BLEND);
+  glDisable(GL_SCISSOR_TEST);
   glViewport(0, 0, TEXTURE_PAGE_WIDTH, TEXTURE_PAGE_HEIGHT);
   glBindVertexArray(m_attributeless_vao_id);
 
@@ -321,8 +333,13 @@ void GPU_HW_OpenGL::FlushRender()
   if (m_batch_vertices.empty())
     return;
 
+  glDisable(GL_CULL_FACE);
+  glDisable(GL_DEPTH_TEST);
+  glEnable(GL_SCISSOR_TEST);
+  glDepthMask(GL_FALSE);
   SetProgram(m_batch_command.texture_enable, m_batch_command.texture_blending_raw);
   SetViewport();
+  SetScissor();
 
   if (m_batch_command.texture_enable)
     m_texture_page_texture->Bind();