gl: Add cairo_gl_surface_create_for_texture()

This creates a Cairo surface from a given texture. This allows using
content previously created using OpenGL inside Cairo.

3 files changed, 86 insertions, 55 deletions

diff --git a/src/cairo-gl-private.h b/src/cairo-gl-private.h
index 803b00ac..8512ab59 100644
--- a/src/cairo-gl-private.h
+++ b/src/cairo-gl-private.h
@@ -71,6 +71,7 @@ typedef struct _cairo_gl_surface {
     int width, height;
 
     GLuint tex; /* GL texture object containing our data. */
+    cairo_bool_t owns_tex; /* TRUE if the surface created the texture */
     GLuint fb; /* GL framebuffer object wrapping our data. */
 } cairo_gl_surface_t;
 
@@ -352,6 +353,6 @@ _cairo_gl_get_program (cairo_gl_context_t *ctx,
 		       cairo_gl_shader_program_t **out_program);
 
 slim_hidden_proto (cairo_gl_surface_create);
-slim_hidden_proto (cairo_gl_surface_make_current);
+slim_hidden_proto (cairo_gl_surface_create_for_texture);
 
 #endif /* CAIRO_GL_PRIVATE_H */
diff --git a/src/cairo-gl-surface.c b/src/cairo-gl-surface.c
index 64c12397..d4028d57 100644
--- a/src/cairo-gl-surface.c
+++ b/src/cairo-gl-surface.c
@@ -356,26 +356,6 @@ _cairo_gl_set_destination (cairo_gl_surface_t *surface)
     glLoadIdentity ();
 }
 
-void
-cairo_gl_surface_make_current (cairo_surface_t *surface)
-{
-    cairo_gl_context_t *ctx = (cairo_gl_context_t *) surface->device;
-
-    cairo_status_t status;
-
-    if (! _cairo_surface_is_gl (surface)) {
-	status = _cairo_surface_set_error (surface,
-		                           CAIRO_STATUS_SURFACE_TYPE_MISMATCH);
-	return;
-    }
-
-    /* external API calling into us is bad */
-    assert (ctx->current_target == NULL);
-    _cairo_gl_set_destination ((cairo_gl_surface_t *) surface);
-    ctx->current_target = NULL;
-}
-slim_hidden_def (cairo_gl_surface_make_current);
-
 cairo_bool_t
 _cairo_gl_operator_is_supported (cairo_operator_t op)
 {
@@ -503,6 +483,7 @@ _cairo_gl_surface_init (cairo_device_t *device,
 static cairo_surface_t *
 _cairo_gl_surface_create_scratch (cairo_gl_context_t   *ctx,
 				  cairo_content_t	content,
+                                  GLuint                texture_id,
 				  int			width,
 				  int			height)
 {
@@ -524,36 +505,42 @@ _cairo_gl_surface_create_scratch (cairo_gl_context_t   *ctx,
     if (height < 1)
 	height = 1;
 
-    switch (content) {
-    default:
-	ASSERT_NOT_REACHED;
-    case CAIRO_CONTENT_COLOR_ALPHA:
-	format = GL_RGBA;
-	break;
-    case CAIRO_CONTENT_ALPHA:
-	/* We want to be trying GL_ALPHA framebuffer objects here. */
-	format = GL_RGBA;
-	break;
-    case CAIRO_CONTENT_COLOR:
-	/* GL_RGB is almost what we want here -- sampling 1 alpha when
-	 * texturing, using 1 as destination alpha factor in blending,
-	 * etc.  However, when filtering with GL_CLAMP_TO_BORDER, the
-	 * alpha channel of the border color will also be clamped to
-	 * 1, when we actually want the border color we explicitly
-	 * specified.  So, we have to store RGBA, and fill the alpha
-	 * channel with 1 when blending.
-	 */
-	format = GL_RGBA;
-	break;
-    }
+    if (texture_id == 0) {
+        switch (content) {
+        default:
+            ASSERT_NOT_REACHED;
+        case CAIRO_CONTENT_COLOR_ALPHA:
+            format = GL_RGBA;
+            break;
+        case CAIRO_CONTENT_ALPHA:
+            /* We want to be trying GL_ALPHA framebuffer objects here. */
+            format = GL_RGBA;
+            break;
+        case CAIRO_CONTENT_COLOR:
+            /* GL_RGB is almost what we want here -- sampling 1 alpha when
+             * texturing, using 1 as destination alpha factor in blending,
+             * etc.  However, when filtering with GL_CLAMP_TO_BORDER, the
+             * alpha channel of the border color will also be clamped to
+             * 1, when we actually want the border color we explicitly
+             * specified.  So, we have to store RGBA, and fill the alpha
+             * channel with 1 when blending.
+             */
+            format = GL_RGBA;
+            break;
+        }
 
-    /* Create the texture used to store the surface's data. */
-    glGenTextures (1, &surface->tex);
-    glBindTexture (ctx->tex_target, surface->tex);
-    glTexParameteri (ctx->tex_target, GL_TEXTURE_MIN_FILTER, GL_NEAREST);
-    glTexParameteri (ctx->tex_target, GL_TEXTURE_MAG_FILTER, GL_NEAREST);
-    glTexImage2D (ctx->tex_target, 0, format, width, height, 0,
-		  format, GL_UNSIGNED_BYTE, NULL);
+        /* Create the texture used to store the surface's data. */
+        glGenTextures (1, &surface->tex);
+        surface->owns_tex = TRUE;
+        glBindTexture (ctx->tex_target, surface->tex);
+        glTexParameteri (ctx->tex_target, GL_TEXTURE_MIN_FILTER, GL_NEAREST);
+        glTexParameteri (ctx->tex_target, GL_TEXTURE_MAG_FILTER, GL_NEAREST);
+        glTexImage2D (ctx->tex_target, 0, format, width, height, 0,
+                      format, GL_UNSIGNED_BYTE, NULL);
+    } else {
+        surface->tex = texture_id;
+        surface->owns_tex = FALSE;
+    }
 
     /* Create a framebuffer object wrapping the texture so that we can render
      * to it.
@@ -627,7 +614,7 @@ cairo_gl_surface_create (cairo_device_t		*abstract_device,
 	return _cairo_surface_create_in_error (status);
 
     surface = (cairo_gl_surface_t *)
-	_cairo_gl_surface_create_scratch (ctx, content, width, height);
+	_cairo_gl_surface_create_scratch (ctx, content, 0, width, height);
     if (unlikely (surface->base.status)) {
 	_cairo_gl_context_release (ctx);
 	return &surface->base;
@@ -647,6 +634,47 @@ cairo_gl_surface_create (cairo_device_t		*abstract_device,
 }
 slim_hidden_def (cairo_gl_surface_create);
 
+cairo_surface_t *
+cairo_gl_surface_create_for_texture (cairo_device_t	*abstract_device,
+                                     unsigned int        texture_id)
+{
+    cairo_gl_context_t *ctx = (cairo_gl_context_t *) abstract_device;
+    cairo_gl_surface_t *surface;
+    cairo_status_t status;
+    int width, height;
+
+    if (ctx == NULL || ctx->base.backend->type != CAIRO_DEVICE_TYPE_GL)
+	return _cairo_surface_create_in_error (_cairo_error (CAIRO_STATUS_SURFACE_TYPE_MISMATCH));
+
+    status = _cairo_gl_context_acquire (abstract_device, &ctx);
+    if (unlikely (status))
+	return _cairo_surface_create_in_error (status);
+
+    glBindTexture (ctx->tex_target, texture_id);
+    glGetTexLevelParameteriv (ctx->tex_target, 0, GL_TEXTURE_WIDTH,  &width );
+    glGetTexLevelParameteriv (ctx->tex_target, 0, GL_TEXTURE_HEIGHT, &height);
+
+    surface = (cairo_gl_surface_t *)
+	_cairo_gl_surface_create_scratch (ctx, CAIRO_CONTENT_COLOR_ALPHA, texture_id, width, height);
+    if (unlikely (surface->base.status)) {
+	_cairo_gl_context_release (ctx);
+	return &surface->base;
+    }
+
+    /* Cairo surfaces start out initialized to transparent (black) */
+    status = _cairo_gl_surface_clear (surface);
+    if (unlikely (status)) {
+	cairo_surface_destroy (&surface->base);
+	_cairo_gl_context_release (ctx);
+	return _cairo_surface_create_in_error (status);
+    }
+
+    _cairo_gl_context_release (ctx);
+
+    return &surface->base;
+}
+slim_hidden_def (cairo_gl_surface_create_for_texture);
+
 void
 cairo_gl_surface_set_size (cairo_surface_t *abstract_surface,
 			   int              width,
@@ -748,7 +776,7 @@ _cairo_gl_surface_create_similar (void		 *abstract_surface,
     if (unlikely (status))
 	return _cairo_surface_create_in_error (status);
 
-    surface = _cairo_gl_surface_create_scratch (ctx, content, width, height);
+    surface = _cairo_gl_surface_create_scratch (ctx, content, 0, width, height);
     _cairo_gl_context_release (ctx);
 
     return surface;
@@ -1006,7 +1034,8 @@ _cairo_gl_surface_finish (void *abstract_surface)
     cairo_gl_context_t *ctx = (cairo_gl_context_t *) surface->base.device;
 
     glDeleteFramebuffersEXT (1, &surface->fb);
-    glDeleteTextures (1, &surface->tex);
+    if (surface->owns_tex)
+        glDeleteTextures (1, &surface->tex);
 
     if (ctx->current_target == surface)
 	ctx->current_target = NULL;
diff --git a/src/cairo-gl.h b/src/cairo-gl.h
index 50e14994..03eb5a40 100644
--- a/src/cairo-gl.h
+++ b/src/cairo-gl.h
@@ -45,8 +45,9 @@ cairo_gl_surface_create (cairo_device_t *device,
 			 cairo_content_t content,
 			 int width, int height);
 
-cairo_public void
-cairo_gl_surface_make_current (cairo_surface_t *surface);
+cairo_public cairo_surface_t *
+cairo_gl_surface_create_for_texture (cairo_device_t *device,
+                                     unsigned int texture_id);
 
 cairo_public void
 cairo_gl_surface_set_size (cairo_surface_t *surface, int width, int height);