From 555fbf479ac9af356446e71bb53187981b865167 Mon Sep 17 00:00:00 2001
From: Dan Paulat <dpaulat@gmail.com>
Date: Sun, 10 Sep 2023 21:44:19 -0500
Subject: [PATCH] Don't call glGenTextures every time the texture atlas updates

---
 scwx-qt/source/scwx/qt/gl/gl_context.cpp      | 23 ++++++++++++++++---
 scwx-qt/source/scwx/qt/util/texture_atlas.cpp |  7 +-----
 scwx-qt/source/scwx/qt/util/texture_atlas.hpp |  8 +++----
 3 files changed, 25 insertions(+), 13 deletions(-)

diff --git a/scwx-qt/source/scwx/qt/gl/gl_context.cpp b/scwx-qt/source/scwx/qt/gl/gl_context.cpp
index 64e2df46..592d12cb 100644
--- a/scwx-qt/source/scwx/qt/gl/gl_context.cpp
+++ b/scwx-qt/source/scwx/qt/gl/gl_context.cpp
@@ -26,11 +26,15 @@ public:
    }
    ~Impl() {}
 
+   void InitializeGL();
+
    static std::size_t
    GetShaderKey(std::initializer_list<std::pair<GLenum, std::string>> shaders);
 
    gl::OpenGLFunctions gl_;
 
+   bool glInitialized_ {false};
+
    std::unordered_map<std::size_t, std::shared_ptr<gl::ShaderProgram>>
               shaderProgramMap_;
    std::mutex shaderProgramMutex_;
@@ -57,6 +61,18 @@ std::uint64_t GlContext::texture_buffer_count() const
    return p->textureBufferCount_;
 }
 
+void GlContext::Impl::InitializeGL()
+{
+   if (glInitialized_)
+   {
+      return;
+   }
+
+   gl_.glGenTextures(1, &textureAtlas_);
+
+   glInitialized_ = true;
+}
+
 std::shared_ptr<gl::ShaderProgram>
 GlContext::GetShaderProgram(const std::string& vertexPath,
                             const std::string& fragmentPath)
@@ -91,15 +107,16 @@ std::shared_ptr<gl::ShaderProgram> GlContext::GetShaderProgram(
 
 GLuint GlContext::GetTextureAtlas()
 {
+   p->InitializeGL();
+
    std::unique_lock lock(p->textureMutex_);
 
    auto& textureAtlas = util::TextureAtlas::Instance();
 
-   if (p->textureAtlas_ == GL_INVALID_INDEX ||
-       p->textureBufferCount_ != textureAtlas.BuildCount())
+   if (p->textureBufferCount_ != textureAtlas.BuildCount())
    {
       p->textureBufferCount_ = textureAtlas.BuildCount();
-      p->textureAtlas_       = textureAtlas.BufferAtlas(p->gl_);
+      textureAtlas.BufferAtlas(p->gl_, p->textureAtlas_);
    }
 
    return p->textureAtlas_;
diff --git a/scwx-qt/source/scwx/qt/util/texture_atlas.cpp b/scwx-qt/source/scwx/qt/util/texture_atlas.cpp
index ad4502db..c6a29d00 100644
--- a/scwx-qt/source/scwx/qt/util/texture_atlas.cpp
+++ b/scwx-qt/source/scwx/qt/util/texture_atlas.cpp
@@ -323,10 +323,8 @@ void TextureAtlas::BuildAtlas(std::size_t width, std::size_t height)
    ++p->buildCount_;
 }
 
-GLuint TextureAtlas::BufferAtlas(gl::OpenGLFunctions& gl)
+void TextureAtlas::BufferAtlas(gl::OpenGLFunctions& gl, GLuint texture)
 {
-   GLuint texture = GL_INVALID_INDEX;
-
    std::shared_lock lock(p->atlasMutex_);
 
    if (p->atlasArray_.size() > 0u && p->atlasArray_[0].width() > 0 &&
@@ -354,7 +352,6 @@ GLuint TextureAtlas::BufferAtlas(gl::OpenGLFunctions& gl)
 
       lock.unlock();
 
-      gl.glGenTextures(1, &texture);
       gl.glBindTexture(GL_TEXTURE_2D_ARRAY, texture);
 
       gl.glTexParameteri(
@@ -375,8 +372,6 @@ GLuint TextureAtlas::BufferAtlas(gl::OpenGLFunctions& gl)
                       GL_UNSIGNED_BYTE,
                       pixelData.data());
    }
-
-   return texture;
 }
 
 TextureAttributes TextureAtlas::GetTextureAttributes(const std::string& name)
diff --git a/scwx-qt/source/scwx/qt/util/texture_atlas.hpp b/scwx-qt/source/scwx/qt/util/texture_atlas.hpp
index 5cc77889..813962d2 100644
--- a/scwx-qt/source/scwx/qt/util/texture_atlas.hpp
+++ b/scwx-qt/source/scwx/qt/util/texture_atlas.hpp
@@ -72,10 +72,10 @@ public:
 
    std::uint64_t BuildCount() const;
 
-   void   RegisterTexture(const std::string& name, const std::string& path);
-   bool   CacheTexture(const std::string& name, const std::string& path);
-   void   BuildAtlas(std::size_t width, std::size_t height);
-   GLuint BufferAtlas(gl::OpenGLFunctions& gl);
+   void RegisterTexture(const std::string& name, const std::string& path);
+   bool CacheTexture(const std::string& name, const std::string& path);
+   void BuildAtlas(std::size_t width, std::size_t height);
+   void BufferAtlas(gl::OpenGLFunctions& gl, GLuint texture);
 
    TextureAttributes GetTextureAttributes(const std::string& name);