more efficient font rendering using glTexSubImage2D

1 files changed, 8 insertions, 3 deletions

diff --git a/crawl-ref/source/glwrapper-ogl.cc b/crawl-ref/source/glwrapper-ogl.cc
index c5b4651045..6e8c935e37 100644
--- a/crawl-ref/source/glwrapper-ogl.cc
+++ b/crawl-ref/source/glwrapper-ogl.cc
@@ -184,7 +184,8 @@ void OGLStateManager::bind_texture(unsigned int texture)
 }
 
 void OGLStateManager::load_texture(unsigned char *pixels, unsigned int width,
-                                   unsigned int height, MipMapOptions mip_opt)
+                                   unsigned int height, MipMapOptions mip_opt,
+                                   int xoffset, int yoffset)
 {
     // Assumptions...
     const unsigned int bpp = 4;
@@ -214,8 +215,12 @@ void OGLStateManager::load_texture(unsigned char *pixels, unsigned int width,
     {
         glTexParameterf(GL_TEXTURE_2D, GL_TEXTURE_MIN_FILTER, GL_NEAREST);
         glTexParameterf(GL_TEXTURE_2D, GL_TEXTURE_MAG_FILTER, GL_NEAREST);
-        glTexImage2D(GL_TEXTURE_2D, 0, bpp, width, height, 0,
-                     texture_format, format, pixels);
+        if( xoffset >= 0 && yoffset >= 0 )
+            glTexSubImage2D(GL_TEXTURE_2D, 0, xoffset, yoffset, width, height,
+                         texture_format, format, pixels);
+        else
+            glTexImage2D(GL_TEXTURE_2D, 0, bpp, width, height, 0,
+                         texture_format, format, pixels);
     }
 }