+
+// Renders the input text at the current location with the current color.
+// The X position of the current location is used to place the left edge of the text image,
+// where the text image bounds are defined as the logical extents of the line of text.
+// The Y position of the current location is used to place the bottom of the text image.
+// You should offset the Y position by the amount returned by gtk_glwidget_font_descent()
+// if you want to place the baseline of the text image at the current Y position.
+// Note: A problem with this function is that if the lower left corner of the text falls
+// just a hair outside of the viewport (meaning the current raster position is invalid),
+// then no text will be rendered. The solution to this is a very hacky one. You can search
+// Google for "glDrawPixels clipping".
+virtual void printString( const char *s ){
+ // The idea for this code initially came from the font-pangoft2.c example that comes with GtkGLExt.
+
+ PangoLayout *layout;
+ PangoRectangle log_rect;
+ FT_Bitmap bitmap;
+ unsigned char *begin_bitmap_buffer;
+ GLfloat color[4];
+ GLint previous_unpack_alignment;
+ GLboolean previous_blend_enabled;
+ GLint previous_blend_func_src;
+ GLint previous_blend_func_dst;
+ GLfloat previous_red_bias;
+ GLfloat previous_green_bias;
+ GLfloat previous_blue_bias;
+ GLfloat previous_alpha_scale;
+
+ layout = pango_layout_new( ft2_context );
+ pango_layout_set_width( layout, -1 ); // -1 no wrapping. All text on one line.
+ pango_layout_set_text( layout, s, -1 ); // -1 null-terminated string.
+ pango_layout_get_extents( layout, NULL, &log_rect );
+
+ if ( log_rect.width > 0 && log_rect.height > 0 ) {
+ bitmap.rows = font_ascent + font_descent;
+ bitmap.width = PANGO_PIXELS_CEIL( log_rect.width );
+ bitmap.pitch = -bitmap.width; // Rendering it "upside down" for OpenGL.
+ begin_bitmap_buffer = (unsigned char *) g_malloc( bitmap.rows * bitmap.width );
+ memset( begin_bitmap_buffer, 0, bitmap.rows * bitmap.width );
+ bitmap.buffer = begin_bitmap_buffer + ( bitmap.rows - 1 ) * bitmap.width; // See pitch above.
+ bitmap.num_grays = 0xff;
+ bitmap.pixel_mode = FT_PIXEL_MODE_GRAY;
+ pango_ft2_render_layout_subpixel( &bitmap, layout, -log_rect.x,
+ y_offset_bitmap_render_pango_units );
+ GlobalOpenGL().m_glGetFloatv( GL_CURRENT_COLOR, color );
+
+ // Save state. I didn't see any OpenGL push/pop operations for these.
+ // Question: Is saving/restoring this state necessary? Being safe.
+ GlobalOpenGL().m_glGetIntegerv( GL_UNPACK_ALIGNMENT, &previous_unpack_alignment );
+ previous_blend_enabled = GlobalOpenGL().m_glIsEnabled( GL_BLEND );
+ GlobalOpenGL().m_glGetIntegerv( GL_BLEND_SRC, &previous_blend_func_src );
+ GlobalOpenGL().m_glGetIntegerv( GL_BLEND_DST, &previous_blend_func_dst );
+ GlobalOpenGL().m_glGetFloatv( GL_RED_BIAS, &previous_red_bias );
+ GlobalOpenGL().m_glGetFloatv( GL_GREEN_BIAS, &previous_green_bias );
+ GlobalOpenGL().m_glGetFloatv( GL_BLUE_BIAS, &previous_blue_bias );
+ GlobalOpenGL().m_glGetFloatv( GL_ALPHA_SCALE, &previous_alpha_scale );
+
+ GlobalOpenGL().m_glPixelStorei( GL_UNPACK_ALIGNMENT, 1 );
+ GlobalOpenGL().m_glEnable( GL_BLEND );
+ GlobalOpenGL().m_glBlendFunc( GL_SRC_ALPHA, GL_ONE_MINUS_SRC_ALPHA );
+ GlobalOpenGL().m_glPixelTransferf( GL_RED_BIAS, color[0] );
+ GlobalOpenGL().m_glPixelTransferf( GL_GREEN_BIAS, color[1] );
+ GlobalOpenGL().m_glPixelTransferf( GL_BLUE_BIAS, color[2] );
+ GlobalOpenGL().m_glPixelTransferf( GL_ALPHA_SCALE, color[3] );
+
+ GlobalOpenGL().m_glDrawPixels( bitmap.width, bitmap.rows,
+ GL_ALPHA, GL_UNSIGNED_BYTE, begin_bitmap_buffer );
+ g_free( begin_bitmap_buffer );
+
+ // Restore state in reverse order of how we set it.
+ GlobalOpenGL().m_glPixelTransferf( GL_ALPHA_SCALE, previous_alpha_scale );
+ GlobalOpenGL().m_glPixelTransferf( GL_BLUE_BIAS, previous_blue_bias );
+ GlobalOpenGL().m_glPixelTransferf( GL_GREEN_BIAS, previous_green_bias );
+ GlobalOpenGL().m_glPixelTransferf( GL_RED_BIAS, previous_red_bias );
+ GlobalOpenGL().m_glBlendFunc( previous_blend_func_src, previous_blend_func_dst );
+ if ( !previous_blend_enabled ) {
+ GlobalOpenGL().m_glDisable( GL_BLEND );
+ }
+ GlobalOpenGL().m_glPixelStorei( GL_UNPACK_ALIGNMENT, previous_unpack_alignment );
+ }
+
+ g_object_unref( G_OBJECT( layout ) );
+}
+
+virtual int getPixelAscent() const {
+ return font_ascent;
+}
+virtual int getPixelDescent() const {
+ return font_descent;
+}
+virtual int getPixelHeight() const {
+ return font_height;
+}
+};
+
+GLFont *glfont_create( const char* font_string ){
+ return new GLFontInternal( font_string );
+}
+
+#endif