- // 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;
-
- if (!_debug_font_created) {
- Error("Programming error: gtk_glwidget_print_string() called but font does not exist; "
- "you should have called gtk_glwidget_create_font() first");
- }
-
- 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);
- qglGetFloatv(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.
- qglGetIntegerv(GL_UNPACK_ALIGNMENT, &previous_unpack_alignment);
- previous_blend_enabled = qglIsEnabled(GL_BLEND);
- qglGetIntegerv(GL_BLEND_SRC, &previous_blend_func_src);
- qglGetIntegerv(GL_BLEND_DST, &previous_blend_func_dst);
- qglGetFloatv(GL_RED_BIAS, &previous_red_bias);
- qglGetFloatv(GL_GREEN_BIAS, &previous_green_bias);
- qglGetFloatv(GL_BLUE_BIAS, &previous_blue_bias);
- qglGetFloatv(GL_ALPHA_SCALE, &previous_alpha_scale);
-
- qglPixelStorei(GL_UNPACK_ALIGNMENT, 1);
- qglEnable(GL_BLEND);
- qglBlendFunc(GL_SRC_ALPHA, GL_ONE_MINUS_SRC_ALPHA);
- qglPixelTransferf(GL_RED_BIAS, color[0]);
- qglPixelTransferf(GL_GREEN_BIAS, color[1]);
- qglPixelTransferf(GL_BLUE_BIAS, color[2]);
- qglPixelTransferf(GL_ALPHA_SCALE, color[3]);
-
- qglDrawPixels(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.
- qglPixelTransferf(GL_ALPHA_SCALE, previous_alpha_scale);
- qglPixelTransferf(GL_BLUE_BIAS, previous_blue_bias);
- qglPixelTransferf(GL_GREEN_BIAS, previous_green_bias);
- qglPixelTransferf(GL_RED_BIAS, previous_red_bias);
- qglBlendFunc(previous_blend_func_src, previous_blend_func_dst);
- if (!previous_blend_enabled) { qglDisable(GL_BLEND); }
- qglPixelStorei(GL_UNPACK_ALIGNMENT, previous_unpack_alignment);
- }
-
- g_object_unref(G_OBJECT(layout));