From 65659e2ab63f028a16cb361769dd5c86e85529b2 Mon Sep 17 00:00:00 2001
From: =?UTF-8?q?=CE=B6eh=20Matt?= <m.moninger.h@gmail.com>
Date: Fri, 7 Sep 2018 10:21:28 +0200
Subject: [PATCH] Fix OpenGL renderer stuttering when loading new textures into
 atlas

---
 .../drawing/engines/opengl/TextureCache.cpp   | 30 +++++++++++++------
 .../drawing/engines/opengl/TextureCache.h     |  1 +
 2 files changed, 22 insertions(+), 9 deletions(-)

diff --git a/src/openrct2-ui/drawing/engines/opengl/TextureCache.cpp b/src/openrct2-ui/drawing/engines/opengl/TextureCache.cpp
index d35faffcb0..211bfb0558 100644
--- a/src/openrct2-ui/drawing/engines/opengl/TextureCache.cpp
+++ b/src/openrct2-ui/drawing/engines/opengl/TextureCache.cpp
@@ -136,6 +136,7 @@ void TextureCache::CreateTextures()
 
         _initialized = true;
         _atlasesTextureIndices = 0;
+        _atlasesTextureCapacity = 0;
     }
 }
 
@@ -169,22 +170,33 @@ void TextureCache::EnlargeAtlasesTexture(GLuint newEntries)
 
     GLuint newIndices = _atlasesTextureIndices + newEntries;
 
-    // Retrieve current array data
-    auto oldPixels = std::vector<char>(_atlasesTextureDimensions * _atlasesTextureDimensions * _atlasesTextureIndices);
-    if (oldPixels.size() > 0)
+    std::vector<char> oldPixels;
+
+    if (newIndices > _atlasesTextureCapacity)
     {
-        glGetTexImage(GL_TEXTURE_2D_ARRAY, 0, GL_RED_INTEGER, GL_UNSIGNED_BYTE, oldPixels.data());
+        // Retrieve current array data, growing buffer.
+        oldPixels.resize(_atlasesTextureDimensions * _atlasesTextureDimensions * _atlasesTextureCapacity);
+        if (oldPixels.size() > 0)
+        {
+            glGetTexImage(GL_TEXTURE_2D_ARRAY, 0, GL_RED_INTEGER, GL_UNSIGNED_BYTE, oldPixels.data());
+        }
+
+        // Initial capacity will be 12 which covers most cases of a fully visible park.
+        _atlasesTextureCapacity = (_atlasesTextureCapacity + 6) << 1;
     }
 
     glBindTexture(GL_TEXTURE_2D_ARRAY, _atlasesTexture);
     glTexImage3D(
-        GL_TEXTURE_2D_ARRAY, 0, GL_R8UI, _atlasesTextureDimensions, _atlasesTextureDimensions, newIndices, 0, GL_RED_INTEGER,
-        GL_UNSIGNED_BYTE, nullptr);
+        GL_TEXTURE_2D_ARRAY, 0, GL_R8UI, _atlasesTextureDimensions, _atlasesTextureDimensions, _atlasesTextureCapacity, 0,
+        GL_RED_INTEGER, GL_UNSIGNED_BYTE, nullptr);
 
     // Restore old data
-    glTexSubImage3D(
-        GL_TEXTURE_2D_ARRAY, 0, 0, 0, 0, _atlasesTextureDimensions, _atlasesTextureDimensions, _atlasesTextureIndices,
-        GL_RED_INTEGER, GL_UNSIGNED_BYTE, oldPixels.data());
+    if (oldPixels.size() > 0)
+    {
+        glTexSubImage3D(
+            GL_TEXTURE_2D_ARRAY, 0, 0, 0, 0, _atlasesTextureDimensions, _atlasesTextureDimensions, _atlasesTextureIndices,
+            GL_RED_INTEGER, GL_UNSIGNED_BYTE, oldPixels.data());
+    }
 
     _atlasesTextureIndices = newIndices;
 }
diff --git a/src/openrct2-ui/drawing/engines/opengl/TextureCache.h b/src/openrct2-ui/drawing/engines/opengl/TextureCache.h
index 69ac59783b..7e60c29a3c 100644
--- a/src/openrct2-ui/drawing/engines/opengl/TextureCache.h
+++ b/src/openrct2-ui/drawing/engines/opengl/TextureCache.h
@@ -189,6 +189,7 @@ private:
 
     GLuint _atlasesTexture = 0;
     GLint _atlasesTextureDimensions = 0;
+    GLuint _atlasesTextureCapacity = 0;
     GLuint _atlasesTextureIndices = 0;
     GLint _atlasesTextureIndicesLimit = 0;
     std::vector<Atlas> _atlases;