text: gltex: add OpenGL text renderer

This adds an OpenGL text renderer. It uses textures to store glyph
information and renders the characters by assembling a vertex-list first.
To improve performance, we use texture-atlases.

Signed-off-by: David Herrmann <dh.herrmann@googlemail.com>

Makefile.am

@@ -88,7 +88,9 @@ SHADERS = \
 	src/static_blend.vert \
 	src/static_blend.frag \
 	src/static_blit.vert \
-	src/static_blit.frag
+	src/static_blit.frag \
+	src/static_gltex.vert \
+	src/static_gltex.frag
 
 EXTRA_DIST += \
 	$(SHADERS)
@@ -142,6 +144,11 @@ libkmscon_core_la_SOURCES += \
 	src/text_bblit.c
 endif
 
+if KMSCON_HAVE_GLES2
+libkmscon_core_la_SOURCES += \
+	src/text_gltex.c
+endif
+
 libkmscon_core_la_CPPFLAGS = \
 	$(AM_CPPFLAGS) \
 	$(GLES2_CFLAGS) \

configure.ac

@@ -459,6 +459,17 @@ fi
 
 AM_CONDITIONAL([KMSCON_HAVE_BBLIT], [test x$bblit_enabled = xyes])
 
+#
+# OpenGL Texture rendering backend
+# This is not really an option but automatically enabled if OpenGLES2 support
+# was selected.
+#
+
+gltex_enabled=no
+if test x$gles2_enabled = xyes ; then
+        gltex_enabled=yes
+fi
+
 #
 # Makefile vars
 # After everything is configured, we correctly substitute the values for the
@@ -518,5 +529,6 @@ AC_MSG_NOTICE([Build configuration:
 
   rendering backends:
 	        bblit: $bblit_enabled
+	        gltex: $gltex_enabled
 
 	Run "make" to start compilation process])

src/main.c

@@ -338,6 +338,7 @@ int main(int argc, char **argv)
 	kmscon_font_pango_load();
 	kmscon_font_freetype2_load();
 	kmscon_text_bblit_load();
+	kmscon_text_gltex_load();
 
 	memset(&app, 0, sizeof(app));
 	ret = setup_app(&app);
@@ -367,6 +368,7 @@ int main(int argc, char **argv)
 	}
 
 	destroy_app(&app);
+	kmscon_text_gltex_unload();
 	kmscon_text_bblit_unload();
 	kmscon_font_freetype2_unload();
 	kmscon_font_pango_unload();
@@ -377,6 +379,7 @@ int main(int argc, char **argv)
 	return EXIT_SUCCESS;
 
 err_unload:
+	kmscon_text_gltex_unload();
 	kmscon_text_bblit_unload();
 	kmscon_font_freetype2_unload();
 	kmscon_font_pango_unload();

src/static_gltex.frag

@@ -0,0 +1,47 @@
+/*
+ * kmscon - Fragment Shader
+ *
+ * Copyright (c) 2011-2012 David Herrmann <dh.herrmann@googlemail.com>
+ * Copyright (c) 2011 University of Tuebingen
+ *
+ * Permission is hereby granted, free of charge, to any person obtaining
+ * a copy of this software and associated documentation files
+ * (the "Software"), to deal in the Software without restriction, including
+ * without limitation the rights to use, copy, modify, merge, publish,
+ * distribute, sublicense, and/or sell copies of the Software, and to
+ * permit persons to whom the Software is furnished to do so, subject to
+ * the following conditions:
+ *
+ * The above copyright notice and this permission notice shall be included
+ * in all copies or substantial portions of the Software.
+ *
+ * THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS
+ * OR IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF
+ * MERCHANTABILITY, FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT.
+ * IN NO EVENT SHALL THE AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY
+ * CLAIM, DAMAGES OR OTHER LIABILITY, WHETHER IN AN ACTION OF CONTRACT,
+ * TORT OR OTHERWISE, ARISING FROM, OUT OF OR IN CONNECTION WITH THE
+ * SOFTWARE OR THE USE OR OTHER DEALINGS IN THE SOFTWARE.
+ */
+
+/*
+ * Fragement Shader
+ * A basic fragment shader which applies a 2D texture and blends foreground and
+ * background colors.
+ */
+
+uniform sampler2D atlas;
+uniform float advance_htex;
+uniform float advance_vtex;
+
+varying vec2 texpos;
+varying vec3 fgcol;
+varying vec3 bgcol;
+
+void main()
+{
+	vec2 pos = vec2(texpos.x * advance_htex, texpos.y * advance_vtex);
+	float alpha = texture2D(atlas, pos).a;
+	vec3 val = alpha * fgcol + (1.0 - alpha) * bgcol;
+	gl_FragColor = vec4(val, 1.0);
+}

src/static_gltex.vert

@@ -0,0 +1,50 @@
+/*
+ * kmscon - Vertex Shader
+ *
+ * Copyright (c) 2011-2012 David Herrmann <dh.herrmann@googlemail.com>
+ * Copyright (c) 2011 University of Tuebingen
+ *
+ * Permission is hereby granted, free of charge, to any person obtaining
+ * a copy of this software and associated documentation files
+ * (the "Software"), to deal in the Software without restriction, including
+ * without limitation the rights to use, copy, modify, merge, publish,
+ * distribute, sublicense, and/or sell copies of the Software, and to
+ * permit persons to whom the Software is furnished to do so, subject to
+ * the following conditions:
+ *
+ * The above copyright notice and this permission notice shall be included
+ * in all copies or substantial portions of the Software.
+ *
+ * THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS
+ * OR IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF
+ * MERCHANTABILITY, FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT.
+ * IN NO EVENT SHALL THE AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY
+ * CLAIM, DAMAGES OR OTHER LIABILITY, WHETHER IN AN ACTION OF CONTRACT,
+ * TORT OR OTHERWISE, ARISING FROM, OUT OF OR IN CONNECTION WITH THE
+ * SOFTWARE OR THE USE OR OTHER DEALINGS IN THE SOFTWARE.
+ */
+
+/*
+ * Vertex Shader
+ * This shader is a very basic vertex shader which forwards all data and
+ * performs basic matrix multiplications.
+ */
+
+uniform mat4 projection;
+
+attribute vec2 position;
+attribute vec2 texture_position;
+attribute vec3 fgcolor;
+attribute vec3 bgcolor;
+
+varying vec2 texpos;
+varying vec3 fgcol;
+varying vec3 bgcol;
+
+void main()
+{
+	gl_Position = projection * vec4(position, 0.0, 1.0);
+	texpos = texture_position;
+	fgcol = fgcolor;
+	bgcol = bgcolor;
+}

src/text.h

@@ -251,4 +251,22 @@ static inline void kmscon_text_bblit_unload(void)
 
 #endif
 
+#ifdef KMSCON_HAVE_GLES2
+
+int kmscon_text_gltex_load(void);
+void kmscon_text_gltex_unload(void);
+
+#else
+
+static inline int kmscon_text_gltex_load(void)
+{
+	return -EOPNOTSUPP;
+}
+
+static inline void kmscon_text_gltex_unload(void)
+{
+}
+
+#endif
+
 #endif /* KMSCON_TEXT_H */

src/text_gltex.c

@@ -0,0 +1,627 @@
+/*
+ * kmscon - OpenGL Textures Text Renderer Backend
+ *
+ * Copyright (c) 2012 David Herrmann <dh.herrmann@googlemail.com>
+ *
+ * Permission is hereby granted, free of charge, to any person obtaining
+ * a copy of this software and associated documentation files
+ * (the "Software"), to deal in the Software without restriction, including
+ * without limitation the rights to use, copy, modify, merge, publish,
+ * distribute, sublicense, and/or sell copies of the Software, and to
+ * permit persons to whom the Software is furnished to do so, subject to
+ * the following conditions:
+ *
+ * The above copyright notice and this permission notice shall be included
+ * in all copies or substantial portions of the Software.
+ *
+ * THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS
+ * OR IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF
+ * MERCHANTABILITY, FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT.
+ * IN NO EVENT SHALL THE AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY
+ * CLAIM, DAMAGES OR OTHER LIABILITY, WHETHER IN AN ACTION OF CONTRACT,
+ * TORT OR OTHERWISE, ARISING FROM, OUT OF OR IN CONNECTION WITH THE
+ * SOFTWARE OR THE USE OR OTHER DEALINGS IN THE SOFTWARE.
+ */
+
+/**
+ * SECTION:text_gltex.c
+ * @short_description: OpenGL Textures Text Renderer Backend
+ * @include: text.h
+ *
+ * Uses OpenGL textures to store glyph information and draws these textures with
+ * a custom fragment shader.
+ * Glyphs are stored in texture-atlases. OpenGL has heavy restrictions on
+ * texture sizes so we need to use multiple atlases. As there is no way to pass
+ * a varying amount of textures to a shader, we need to render the screen for
+ * each atlas we have.
+ */
+
+#define GL_GLEXT_PROTOTYPES
+
+#include <errno.h>
+#include <GLES2/gl2.h>
+#include <GLES2/gl2ext.h>
+#include <limits.h>
+#include <stdbool.h>
+#include <stdlib.h>
+#include <string.h>
+#include "log.h"
+#include "static_gl.h"
+#include "static_misc.h"
+#include "text.h"
+#include "unicode.h"
+#include "uterm.h"
+
+#define LOG_SUBSYSTEM "text_gltex"
+
+struct atlas {
+	struct kmscon_dlist list;
+
+	GLuint tex;
+	unsigned int height;
+	unsigned int width;
+	unsigned int count;
+	unsigned int fill;
+
+	unsigned int cache_size;
+	unsigned int cache_num;
+	GLfloat *cache_pos;
+	GLfloat *cache_texpos;
+	GLfloat *cache_fgcol;
+	GLfloat *cache_bgcol;
+
+	GLfloat advance_htex;
+	GLfloat advance_vtex;
+};
+
+struct glyph {
+	const struct kmscon_glyph *glyph;
+	struct atlas *atlas;
+	unsigned int texoff;
+};
+
+#define GLYPH_WIDTH(gly) ((gly)->glyph->buf.width)
+#define GLYPH_HEIGHT(gly) ((gly)->glyph->buf.height)
+#define GLYPH_STRIDE(gly) ((gly)->glyph->buf.stride)
+#define GLYPH_DATA(gly) ((gly)->glyph->buf.data)
+
+struct gltex {
+	struct kmscon_hashtable *glyphs;
+	unsigned int max_tex_size;
+
+	struct kmscon_dlist atlases;
+
+	GLfloat advance_x;
+	GLfloat advance_y;
+
+	struct gl_shader *shader;
+	GLuint uni_proj;
+	GLuint uni_atlas;
+	GLuint uni_advance_htex;
+	GLuint uni_advance_vtex;
+};
+
+#define FONT_WIDTH(txt) ((txt)->font->attr.width)
+#define FONT_HEIGHT(txt) ((txt)->font->attr.height)
+
+#define SCREEN_WIDTH(txt) uterm_screen_width((txt)->screen)
+#define SCREEN_HEIGHT(txt) uterm_screen_height((txt)->screen)
+
+static int gltex_init(struct kmscon_text *txt)
+{
+	struct gltex *gt;
+
+	gt = malloc(sizeof(*gt));
+	if (!gt)
+		return -ENOMEM;
+
+	txt->data = gt;
+	return 0;
+}
+
+static void gltex_destroy(struct kmscon_text *txt)
+{
+	struct gltex *gt = txt->data;
+
+	free(gt);
+}
+
+static void free_glyph(void *data)
+{
+	struct glyph *glyph = data;
+
+	free(glyph);
+}
+
+extern const char *gl_static_gltex_vert;
+extern const char *gl_static_gltex_frag;
+
+static int gltex_set(struct kmscon_text *txt)
+{
+	struct gltex *gt = txt->data;
+	int ret;
+	static char *attr[] = { "position", "texture_position",
+				"fgcolor", "bgcolor" };
+	unsigned int sw, sh;
+	GLint s;
+
+	memset(gt, 0, sizeof(*gt));
+	kmscon_dlist_init(&gt->atlases);
+
+	ret = kmscon_hashtable_new(&gt->glyphs, kmscon_direct_hash,
+				   kmscon_direct_equal, NULL,
+				   free_glyph);
+	if (ret)
+		return ret;
+
+	ret = uterm_screen_use(txt->screen);
+	if (ret)
+		goto err_htable;
+
+	gl_clear_error();
+
+	ret = gl_shader_new(&gt->shader, gl_static_gltex_vert,
+			    gl_static_gltex_frag, attr, 4, log_llog);
+	if (ret)
+		goto err_htable;
+
+	gt->uni_proj = gl_shader_get_uniform(gt->shader, "projection");
+	gt->uni_atlas = gl_shader_get_uniform(gt->shader, "atlas");
+	gt->uni_advance_htex = gl_shader_get_uniform(gt->shader,
+						     "advance_htex");
+	gt->uni_advance_vtex = gl_shader_get_uniform(gt->shader,
+						     "advance_vtex");
+
+	if (gl_has_error(gt->shader)) {
+		log_warning("cannot create shader");
+		goto err_shader;
+	}
+
+	sw = SCREEN_WIDTH(txt);
+	sh = SCREEN_HEIGHT(txt);
+
+	txt->cols = sw / FONT_WIDTH(txt);
+	txt->rows = sh / FONT_HEIGHT(txt);
+
+	glGetIntegerv(GL_MAX_TEXTURE_SIZE, &s);
+	if (s <= 0)
+		s = 64;
+	else if (s > 2048)
+		s = 2048;
+	gt->max_tex_size = s;
+
+	gl_clear_error();
+
+	return 0;
+
+err_shader:
+	gl_shader_unref(gt->shader);
+err_htable:
+	kmscon_hashtable_free(gt->glyphs);
+	return ret;
+}
+
+static void gltex_unset(struct kmscon_text *txt)
+{
+	struct gltex *gt = txt->data;
+	int ret;
+	struct kmscon_dlist *iter;
+	struct atlas *atlas;
+	bool gl = true;
+
+	ret = uterm_screen_use(txt->screen);
+	if (ret) {
+		gl = false;
+		log_warning("cannot activate OpenGL-CTX during destruction");
+	}
+
+	kmscon_hashtable_free(gt->glyphs);
+
+	while (!kmscon_dlist_empty(&gt->atlases)) {
+		iter = gt->atlases.next;
+		kmscon_dlist_unlink(iter);
+		atlas = kmscon_dlist_entry(iter, struct atlas, list);
+
+		free(atlas->cache_pos);
+		free(atlas->cache_texpos);
+		free(atlas->cache_fgcol);
+		free(atlas->cache_bgcol);
+
+		if (gl)
+			gl_tex_free(&atlas->tex, 1);
+	}
+
+	if (gl) {
+		gl_shader_unref(gt->shader);
+
+		gl_clear_error();
+	}
+}
+
+static unsigned int next_pow2(unsigned int num)
+{
+	int i;
+
+	if (!num)
+		return num;
+
+	--num;
+	for (i = 1; i < sizeof(unsigned int) * CHAR_BIT; i <<= 1)
+		num = num | num >> i;
+
+	return num + 1;
+}
+
+/* returns an atlas with at least 1 free glyph position; NULL on error */
+static struct atlas *get_atlas(struct kmscon_text *txt)
+{
+	struct gltex *gt = txt->data;
+	struct atlas *atlas;
+	size_t newsize;
+	unsigned int width, height, nsize;
+	GLenum err;
+
+	/* check whether the last added atlas has still room for one glyph */
+	if (!kmscon_dlist_empty(&gt->atlases)) {
+		atlas = kmscon_dlist_entry(gt->atlases.next, struct atlas,
+					   list);
+		if (atlas->fill < atlas->count)
+			return atlas;
+	}
+
+	/* all atlases are full so we have to create a new atlas */
+	atlas = malloc(sizeof(*atlas));
+	if (!atlas)
+		return NULL;
+	memset(atlas, 0, sizeof(*atlas));
+
+	gl_clear_error();
+
+	gl_tex_new(&atlas->tex, 1);
+	err = glGetError();
+	if (err != GL_NO_ERROR || !atlas->tex) {
+		gl_clear_error();
+		log_warning("cannot create new OpenGL texture: %d", err);
+		goto err_free;
+	}
+
+	newsize = gt->max_tex_size / FONT_WIDTH(txt);
+	if (newsize < 1)
+		newsize = 1;
+
+	/* OpenGL texture sizes are heavily restricted so we need to find a
+	 * valid texture size that is big enough to hold as many glyphs as
+	 * possible but at least 1 */
+try_next:
+	width = next_pow2(FONT_WIDTH(txt) * newsize);
+	height = next_pow2(FONT_HEIGHT(txt));
+
+	gl_clear_error();
+
+	glBindTexture(GL_TEXTURE_2D, atlas->tex);
+	glTexImage2D(GL_TEXTURE_2D, 0, GL_ALPHA, width, height,
+		     0, GL_ALPHA, GL_UNSIGNED_BYTE, NULL);
+
+	err = glGetError();
+	if (err != GL_NO_ERROR) {
+		if (newsize > 1) {
+			--newsize;
+			goto try_next;
+		}
+		gl_clear_error();
+		log_warning("OpenGL textures too small for a single glyph (%d)",
+			    err);
+		goto err_tex;
+	}
+
+	log_debug("new atlas of size %ux%u for %u", width, height, newsize);
+
+	nsize = txt->cols * txt->rows;
+
+	atlas->cache_pos = malloc(sizeof(GLfloat) * nsize * 2 * 6);
+	if (!atlas->cache_pos)
+		goto err_mem;
+
+	atlas->cache_texpos = malloc(sizeof(GLfloat) * nsize * 2 * 6);
+	if (!atlas->cache_texpos)
+		goto err_mem;
+
+	atlas->cache_fgcol = malloc(sizeof(GLfloat) * nsize * 3 * 6);
+	if (!atlas->cache_fgcol)
+		goto err_mem;
+
+	atlas->cache_bgcol = malloc(sizeof(GLfloat) * nsize * 3 * 6);
+	if (!atlas->cache_bgcol)
+		goto err_mem;
+
+	atlas->cache_size = nsize;
+	atlas->count = newsize;
+	atlas->width = width;
+	atlas->height = height;
+	atlas->advance_htex = 1.0 / atlas->width * FONT_WIDTH(txt);
+	atlas->advance_vtex = 1.0 / atlas->height * FONT_HEIGHT(txt);
+
+	kmscon_dlist_link(&gt->atlases, &atlas->list);
+	return atlas;
+
+err_mem:
+	free(atlas->cache_pos);
+	free(atlas->cache_texpos);
+	free(atlas->cache_fgcol);
+	free(atlas->cache_bgcol);
+err_tex:
+	gl_tex_free(&atlas->tex, 1);
+err_free:
+	free(atlas);
+	return NULL;
+}
+
+static int find_glyph(struct kmscon_text *txt, struct glyph **out,
+		      kmscon_symbol_t ch)
+{
+	struct gltex *gt = txt->data;
+	struct atlas *atlas;
+	struct glyph *glyph;
+	bool res;
+	int ret;
+	GLenum err;
+
+	res = kmscon_hashtable_find(gt->glyphs, (void**)&glyph,
+				    (void*)(unsigned long)ch);
+	if (res) {
+		*out = glyph;
+		return 0;
+	}
+
+	atlas = get_atlas(txt);
+	if (!atlas)
+		return -EFAULT;
+
+	glyph = malloc(sizeof(*glyph));
+	if (!glyph)
+		return -ENOMEM;
+	memset(glyph, 0, sizeof(*glyph));
+
+	if (ch == 0 || ch == ' ') {
+		ret = kmscon_font_render_empty(txt->font, &glyph->glyph);
+	} else {
+		ret = kmscon_font_render(txt->font, ch, &glyph->glyph);
+	}
+
+	if (ret) {
+		ret = kmscon_font_render_inval(txt->font, &glyph->glyph);
+		if (ret)
+			goto err_free;
+	}
+
+	gl_clear_error();
+
+	glBindTexture(GL_TEXTURE_2D, atlas->tex);
+	glPixelStorei(GL_UNPACK_ALIGNMENT, 1);
+	glPixelStorei(GL_UNPACK_ROW_LENGTH, GLYPH_STRIDE(glyph));
+	glTexSubImage2D(GL_TEXTURE_2D, 0,
+			FONT_WIDTH(txt) * atlas->fill, 0,
+			GLYPH_WIDTH(glyph),
+			GLYPH_HEIGHT(glyph),
+			GL_ALPHA, GL_UNSIGNED_BYTE,
+			GLYPH_DATA(glyph));
+	glPixelStorei(GL_UNPACK_ROW_LENGTH, 0);
+	glPixelStorei(GL_UNPACK_ALIGNMENT, 4);
+
+	err = glGetError();
+	if (err != GL_NO_ERROR) {
+		gl_clear_error();
+		log_warning("cannot load glyph data into OpenGL texture (%d)",
+			    err);
+		ret = -EFAULT;
+		goto err_free;
+	}
+
+	glyph->atlas = atlas;
+	glyph->texoff = atlas->fill;
+
+	ret = kmscon_hashtable_insert(gt->glyphs, (void*)(long)ch, glyph);
+	if (ret)
+		goto err_free;
+
+	++atlas->fill;
+
+	*out = glyph;
+	return 0;
+
+err_free:
+	free(glyph);
+	return ret;
+}
+
+static int gltex_prepare(struct kmscon_text *txt)
+{
+	struct gltex *gt = txt->data;
+	struct atlas *atlas;
+	struct kmscon_dlist *iter;
+	unsigned int sw, sh;
+	int ret;
+
+	ret = uterm_screen_use(txt->screen);
+	if (ret)
+		return ret;
+
+	kmscon_dlist_for_each(iter, &gt->atlases) {
+		atlas = kmscon_dlist_entry(iter, struct atlas, list);
+
+		atlas->cache_num = 0;
+	}
+
+	sw = SCREEN_WIDTH(txt);
+	sh = SCREEN_HEIGHT(txt);
+
+	gt->advance_x = 2.0 / sw * FONT_WIDTH(txt);
+	gt->advance_y = 2.0 / sh * FONT_HEIGHT(txt);
+
+	return 0;
+}
+
+static int gltex_draw(struct kmscon_text *txt, kmscon_symbol_t ch,
+		      unsigned int posx, unsigned int posy,
+		      const struct font_char_attr *attr)
+{
+	struct gltex *gt = txt->data;
+	struct atlas *atlas;
+	struct glyph *glyph;
+	int ret, i, idx;
+
+	ret = find_glyph(txt, &glyph, ch);
+	if (ret)
+		return ret;
+	atlas = glyph->atlas;
+
+	if (atlas->cache_num >= atlas->cache_size)
+		return -ERANGE;
+
+	atlas->cache_pos[atlas->cache_num * 2 * 6 + 0] =
+		gt->advance_x * posx - 1;
+	atlas->cache_pos[atlas->cache_num * 2 * 6 + 1] =
+		gt->advance_y * posy - 1;
+	atlas->cache_pos[atlas->cache_num * 2 * 6 + 2] =
+		gt->advance_x * posx - 1;
+	atlas->cache_pos[atlas->cache_num * 2 * 6 + 3] =
+		gt->advance_y * posy + gt->advance_y - 1;
+	atlas->cache_pos[atlas->cache_num * 2 * 6 + 4] =
+		gt->advance_x * posx + gt->advance_x - 1;
+	atlas->cache_pos[atlas->cache_num * 2 * 6 + 5] =
+		gt->advance_y * posy + gt->advance_y - 1;
+
+	atlas->cache_pos[atlas->cache_num * 2 * 6 + 6] =
+		gt->advance_x * posx - 1;
+	atlas->cache_pos[atlas->cache_num * 2 * 6 + 7] =
+		gt->advance_y * posy - 1;
+	atlas->cache_pos[atlas->cache_num * 2 * 6 + 8] =
+		gt->advance_x * posx + gt->advance_x - 1;
+	atlas->cache_pos[atlas->cache_num * 2 * 6 + 9] =
+		gt->advance_y * posy + gt->advance_y - 1;
+	atlas->cache_pos[atlas->cache_num * 2 * 6 + 10] =
+		gt->advance_x * posx + gt->advance_x - 1;
+	atlas->cache_pos[atlas->cache_num * 2 * 6 + 11] =
+		gt->advance_y * posy - 1;
+
+	atlas->cache_texpos[atlas->cache_num * 2 * 6 + 0] = glyph->texoff;
+	atlas->cache_texpos[atlas->cache_num * 2 * 6 + 1] = 0.0;
+	atlas->cache_texpos[atlas->cache_num * 2 * 6 + 2] = glyph->texoff;
+	atlas->cache_texpos[atlas->cache_num * 2 * 6 + 3] = 1.0;
+	atlas->cache_texpos[atlas->cache_num * 2 * 6 + 4] = glyph->texoff + 1;
+	atlas->cache_texpos[atlas->cache_num * 2 * 6 + 5] = 1.0;
+
+	atlas->cache_texpos[atlas->cache_num * 2 * 6 + 6] = glyph->texoff;
+	atlas->cache_texpos[atlas->cache_num * 2 * 6 + 7] = 0.0;
+	atlas->cache_texpos[atlas->cache_num * 2 * 6 + 8] = glyph->texoff + 1;
+	atlas->cache_texpos[atlas->cache_num * 2 * 6 + 9] = 1.0;
+	atlas->cache_texpos[atlas->cache_num * 2 * 6 + 10] = glyph->texoff + 1;
+	atlas->cache_texpos[atlas->cache_num * 2 * 6 + 11] = 0.0;
+
+	for (i = 0; i < 6; ++i) {
+		idx = atlas->cache_num * 3 * 6 + i * 3;
+		if (attr->inverse) {
+			atlas->cache_fgcol[idx + 0] = attr->br / 255.0;
+			atlas->cache_fgcol[idx + 1] = attr->bg / 255.0;
+			atlas->cache_fgcol[idx + 2] = attr->bb / 255.0;
+			atlas->cache_bgcol[idx + 0] = attr->fr / 255.0;
+			atlas->cache_bgcol[idx + 1] = attr->fg / 255.0;
+			atlas->cache_bgcol[idx + 2] = attr->fb / 255.0;
+		} else {
+			atlas->cache_fgcol[idx + 0] = attr->fr / 255.0;
+			atlas->cache_fgcol[idx + 1] = attr->fg / 255.0;
+			atlas->cache_fgcol[idx + 2] = attr->fb / 255.0;
+			atlas->cache_bgcol[idx + 0] = attr->br / 255.0;
+			atlas->cache_bgcol[idx + 1] = attr->bg / 255.0;
+			atlas->cache_bgcol[idx + 2] = attr->bb / 255.0;
+		}
+	}
+
+	++atlas->cache_num;
+
+	return 0;
+}
+
+static int gltex_render(struct kmscon_text *txt)
+{
+	struct gltex *gt = txt->data;
+	struct atlas *atlas;
+	struct kmscon_dlist *iter;
+	float mat[16];
+
+	gl_clear_error();
+
+	gl_shader_use(gt->shader);
+
+	glViewport(0, 0, SCREEN_WIDTH(txt), SCREEN_HEIGHT(txt));
+	glDisable(GL_BLEND);
+
+	gl_m4_identity(mat);
+	glUniformMatrix4fv(gt->uni_proj, 1, GL_FALSE, mat);
+
+	glEnableVertexAttribArray(0);
+	glEnableVertexAttribArray(1);
+	glEnableVertexAttribArray(2);
+	glEnableVertexAttribArray(3);
+
+	glActiveTexture(GL_TEXTURE0);
+	glUniform1i(gt->uni_atlas, 0);
+
+	kmscon_dlist_for_each(iter, &gt->atlases) {
+		atlas = kmscon_dlist_entry(iter, struct atlas, list);
+		if (!atlas->cache_num)
+			continue;
+
+		glBindTexture(GL_TEXTURE_2D, atlas->tex);
+		glUniform1f(gt->uni_advance_htex, atlas->advance_htex);
+		glUniform1f(gt->uni_advance_vtex, atlas->advance_vtex);
+
+		glVertexAttribPointer(0, 2, GL_FLOAT, GL_FALSE, 0, atlas->cache_pos);
+		glVertexAttribPointer(1, 2, GL_FLOAT, GL_FALSE, 0, atlas->cache_texpos);
+		glVertexAttribPointer(2, 3, GL_FLOAT, GL_FALSE, 0, atlas->cache_fgcol);
+		glVertexAttribPointer(3, 3, GL_FLOAT, GL_FALSE, 0, atlas->cache_bgcol);
+		glDrawArrays(GL_TRIANGLES, 0, 6 * atlas->cache_num);
+	}
+
+	glDisableVertexAttribArray(0);
+	glDisableVertexAttribArray(1);
+	glDisableVertexAttribArray(2);
+	glDisableVertexAttribArray(3);
+
+	if (gl_has_error(gt->shader)) {
+		log_warning("rendering console caused OpenGL errors");
+		return -EFAULT;
+	}
+
+	return 0;
+}
+
+static const struct kmscon_text_ops kmscon_text_gltex_ops = {
+	.name = "gltex",
+	.init = gltex_init,
+	.destroy = gltex_destroy,
+	.set = gltex_set,
+	.unset = gltex_unset,
+	.prepare = gltex_prepare,
+	.draw = gltex_draw,
+	.render = gltex_render,
+	.abort = NULL,
+};
+
+int kmscon_text_gltex_load(void)
+{
+	int ret;
+
+	ret = kmscon_text_register(&kmscon_text_gltex_ops);
+	if (ret) {
+		log_error("cannot register gltex renderer");
+		return ret;
+	}
+
+	return 0;
+}
+
+void kmscon_text_gltex_unload(void)
+{
+	kmscon_text_unregister(kmscon_text_gltex_ops.name);
+}