[cogl-shader] Make get_info_log() slightly nicer

The cogl_shader_get_info_log() function is very inconvenient for
language bindings and for regular use, as it requires a static
buffer to be filled -- basically just providing a wrapper around
glGetInfoLogARB().

Since COGL aims to be a more convenient API than raw GL we should
just make cogl_shader_get_info_log() return an allocated string
with the GLSL compiler log.

clutter/clutter-shader.c

@@ -451,16 +451,22 @@ clutter_shader_glsl_bind (ClutterShader      *self,
   cogl_shader_compile (shader);
   if (!cogl_shader_is_compiled (shader))
     {
-      gchar error_buf[512];
+      gchar *log_buf;
 
-      cogl_shader_get_info_log (shader, 512, error_buf);
+      log_buf = cogl_shader_get_info_log (shader);
 
+      /* translators: the first %s is the type of the shader, either
+       * Vertex shader or Fragment shader; the second %s is the actual
+       * error as reported by COGL
+       */
       g_set_error (error, CLUTTER_SHADER_ERROR,
                    CLUTTER_SHADER_ERROR_COMPILE,
                    _("%s compilation failed: %s"),
                    shader_type == CLUTTER_VERTEX_SHADER ? _("Vertex shader")
                                                         : _("Fragment shader"),
-                   error_buf);
+                   log_buf);
+
+      g_free (log_buf);
 
       return FALSE;
     }

clutter/cogl/cogl-shader.h

@@ -106,7 +106,7 @@ gboolean        cogl_is_shader               (CoglHandle          handle);
  * one.
  */
 void            cogl_shader_source            (CoglHandle         shader,
-                                               const char        *source);
+                                               const gchar       *source);
 /**
  * cogl_shader_compile:
  * @handle: #CoglHandle for a shader.
@@ -119,17 +119,16 @@ void            cogl_shader_compile           (CoglHandle         handle);
 /**
  * cogl_shader_get_info_log:
  * @handle: #CoglHandle for a shader.
- * @size: maximum number of bytes to retrieve.
- * @buffer: location for info log.
  *
  * Retrieves the information log for a coglobject, can be used in conjunction
- * with #cogl_shader_get_parameteriv to retrieve the compiler warnings/error
+ * with cogl_shader_get_parameteriv() to retrieve the compiler warnings/error
  * messages that caused a shader to not compile correctly, mainly useful for
  * debugging purposes.
+ *
+ * Return value: a newly allocated string containing the info log. Use
+ *   g_free() to free it
  */
-void            cogl_shader_get_info_log      (CoglHandle         handle,
-                                               size_t             size,
-                                               char              *buffer);
+gchar *         cogl_shader_get_info_log      (CoglHandle         handle);
 
 /**
  * cogl_shader_get_type:

clutter/cogl/gl/cogl-shader.c

@@ -108,22 +108,23 @@ cogl_shader_compile (CoglHandle handle)
   glCompileShaderARB (shader->gl_handle);
 }
 
-void
-cogl_shader_get_info_log (CoglHandle  handle,
-                          size_t      size,
-                          char       *buffer)
+gchar *
+cogl_shader_get_info_log (CoglHandle handle)
 {
   CoglShader *shader;
+  char buffer[512];
   int len;
-  _COGL_GET_CONTEXT (ctx, NO_RETVAL);
+  _COGL_GET_CONTEXT (ctx, NULL);
 
   if (!cogl_is_shader (handle))
-    return;
+    return NULL;
 
   shader = _cogl_shader_pointer_from_handle (handle);
 
-  glGetInfoLogARB (shader->gl_handle, size-1, &len, buffer);
+  glGetInfoLogARB (shader->gl_handle, 511, &len, buffer);
   buffer[len]='\0';
+
+  return g_strdup (buffer);
 }
 
 CoglShaderType

clutter/cogl/gles/cogl-shader.c

@@ -99,22 +99,23 @@ cogl_shader_compile (CoglHandle handle)
   glCompileShader (shader->gl_handle);
 }
 
-void
-cogl_shader_get_info_log (CoglHandle  handle,
-                          size_t      size,
-                          char       *buffer)
+gchar *
+cogl_shader_get_info_log (CoglHandle handle)
 {
   CoglShader *shader;
+  char buffer[512]
   int len = 0;
-  _COGL_GET_CONTEXT (ctx, NO_RETVAL);
+  _COGL_GET_CONTEXT (ctx, NULL);
 
   if (!cogl_is_shader (handle))
-    return;
+    return NULL;
 
   shader = _cogl_shader_pointer_from_handle (handle);
 
-  glGetShaderInfoLog (shader->gl_handle, size - 1, &len, buffer);
+  glGetShaderInfoLog (shader->gl_handle, 511, &len, buffer);
   buffer[len] = '\0';
+
+  return g_strdup (buffer);
 }
 
 CoglShaderType