ProgramShaderCache: Create a FBO for shared contexts to draw into

This way it allows us to use surfaceless contexts in EGL/GLX. It also
ensures that the shared context shares a similar setup to the main
context's framebuffer, potentially reducing the number of variants a
driver needs to generate.

2 files changed, 37 insertions, 0 deletions

diff --git a/Source/Core/VideoBackends/OGL/ProgramShaderCache.cpp b/Source/Core/VideoBackends/OGL/ProgramShaderCache.cpp
index c467115534..a4a0a8bf08 100644
--- a/Source/Core/VideoBackends/OGL/ProgramShaderCache.cpp
+++ b/Source/Core/VideoBackends/OGL/ProgramShaderCache.cpp
@@ -1175,6 +1175,24 @@ void ProgramShaderCache::UberShaderCompileWorkItem::Retrieve()
 
 void ProgramShaderCache::CreatePrerenderArrays(SharedContextData* data)
 {
+  // Create a framebuffer object to render into.
+  // This is because in EGL, and potentially GLX, we have a surfaceless context.
+  glGenTextures(1, &data->prerender_FBO_tex);
+  glBindTexture(GL_TEXTURE_2D_ARRAY, data->prerender_FBO_tex);
+  glTexImage3D(GL_TEXTURE_2D_ARRAY, 0, GL_RGBA, 1, 1, 1, 0, GL_RGBA, GL_UNSIGNED_BYTE, nullptr);
+  glTexParameteri(GL_TEXTURE_2D_ARRAY, GL_TEXTURE_MAX_LEVEL, 1);
+  glTexParameteri(GL_TEXTURE_2D_ARRAY, GL_TEXTURE_MIN_FILTER, GL_LINEAR);
+  glGenTextures(1, &data->prerender_FBO_depth);
+  glBindTexture(GL_TEXTURE_2D_ARRAY, data->prerender_FBO_depth);
+  glTexImage3D(GL_TEXTURE_2D_ARRAY, 0, GL_DEPTH_COMPONENT32F, 1, 1, 1, 0, GL_DEPTH_COMPONENT,
+               GL_FLOAT, nullptr);
+  glTexParameteri(GL_TEXTURE_2D_ARRAY, GL_TEXTURE_MAX_LEVEL, 1);
+  glTexParameteri(GL_TEXTURE_2D_ARRAY, GL_TEXTURE_MIN_FILTER, GL_LINEAR);
+  glGenFramebuffers(1, &data->prerender_FBO);
+  glBindFramebuffer(GL_FRAMEBUFFER, data->prerender_FBO);
+  glFramebufferTextureLayer(GL_FRAMEBUFFER, GL_COLOR_ATTACHMENT0, data->prerender_FBO_tex, 0, 0);
+  glFramebufferTextureLayer(GL_FRAMEBUFFER, GL_DEPTH_ATTACHMENT, data->prerender_FBO_depth, 0, 0);
+
   // Create VAO for the prerender vertices.
   // We don't use the normal VAO map, since we need to change the VBO pointer.
   glGenVertexArrays(1, &data->prerender_VAO);
@@ -1257,6 +1275,22 @@ void ProgramShaderCache::DestroyPrerenderArrays(SharedContextData* data)
     glDeleteBuffers(1, &data->prerender_IBO);
     data->prerender_IBO = 0;
   }
+  if (data->prerender_FBO)
+  {
+    glBindFramebuffer(GL_FRAMEBUFFER, 0);
+    glDeleteFramebuffers(1, &data->prerender_FBO);
+    data->prerender_FBO = 0;
+  }
+  if (data->prerender_FBO_tex)
+  {
+    glDeleteTextures(1, &data->prerender_FBO_tex);
+    data->prerender_FBO_tex = 0;
+  }
+  if (data->prerender_FBO_depth)
+  {
+    glDeleteTextures(1, &data->prerender_FBO_depth);
+    data->prerender_FBO_depth = 0;
+  }
 }
 
 void ProgramShaderCache::DrawPrerenderArray(const SHADER& shader, u32 primitive_type)
diff --git a/Source/Core/VideoBackends/OGL/ProgramShaderCache.h b/Source/Core/VideoBackends/OGL/ProgramShaderCache.h
index 61f2f68fdc..41b1d4bb41 100644
--- a/Source/Core/VideoBackends/OGL/ProgramShaderCache.h
+++ b/Source/Core/VideoBackends/OGL/ProgramShaderCache.h
@@ -154,6 +154,9 @@ private:
   struct SharedContextData
   {
     std::unique_ptr<cInterfaceBase> context;
+    GLuint prerender_FBO;
+    GLuint prerender_FBO_tex;
+    GLuint prerender_FBO_depth;
     GLuint prerender_VBO;
     GLuint prerender_VAO;
     GLuint prerender_IBO;