reftests: Add a testcase for GtkGLArea::allowed-apis

See code comments for how it uses GL commands that should fail with GLES.

Related: !6520

testsuite/reftests/glarea-gl-only.c

@@ -0,0 +1,82 @@
+#include <gtk/gtk.h>
+#include <epoxy/gl.h>
+
+/* A png for a red/yellow checkerboard */
+static const char image_data[] = {
+  0211, 0120, 0116, 0107, 0015, 0012, 0032, 0012, 0000, 0000, 0000, 0015, 0111, 0110, 0104, 0122,
+  0000, 0000, 0000, 0040, 0000, 0000, 0000, 0040, 0001, 0003, 0000, 0000, 0000, 0111, 0264, 0350,
+  0267, 0000, 0000, 0000, 0006, 0120, 0114, 0124, 0105, 0377, 0000, 0000, 0377, 0340, 0000, 0241,
+  0105, 0325, 0002, 0000, 0000, 0000, 0025, 0111, 0104, 0101, 0124, 0010, 0327, 0143, 0230, 0011,
+  0004, 0014, 0151, 0100, 0000, 0041, 0300, 0334, 0101, 0044, 0006, 0000, 0355, 0275, 0077, 0301,
+  0347, 0173, 0153, 0007, 0000, 0000, 0000, 0000, 0111, 0105, 0116, 0104, 0256, 0102, 0140, 0202
+};
+
+G_MODULE_EXPORT gboolean
+render_orange_glonly (GtkWidget    *glarea,
+                      GdkGLContext *context)
+{
+  GdkTexture *texture;
+  GdkTextureDownloader *downloader;
+  GBytes *bytes; 
+  gsize stride, width, height;
+  GLuint tex_id, fb_id;
+
+  gdk_gl_context_make_current (context);
+
+  /* Clear to green, so that errors in the following code cause a problem */
+  glClearColor (0.0, 1.0, 0.0, 1.0);
+  glClear (GL_COLOR_BUFFER_BIT);
+
+  /* load the checkerboard image */
+  bytes = g_bytes_new_static (image_data, G_N_ELEMENTS (image_data));
+  texture = gdk_texture_new_from_bytes (bytes, NULL);
+  g_bytes_unref (bytes);
+  width = gdk_texture_get_width (texture);
+  height = gdk_texture_get_height (texture);
+  downloader = gdk_texture_downloader_new (texture);
+  /* Make sure we use a format that GLES does *NOT* support.
+   * And that must include extensions.
+   * But GL_EXT_texture_norm16 does support RGB16 as a source, which
+   * is why we also use mipmaps below. */
+  gdk_texture_downloader_set_format (downloader, GDK_MEMORY_R16G16B16);
+  bytes = gdk_texture_downloader_download_bytes (downloader, &stride);
+  g_object_unref (texture);
+  gdk_texture_downloader_free (downloader);
+
+  glGenTextures (1, &tex_id);
+  glActiveTexture (GL_TEXTURE0);
+  glBindTexture (GL_TEXTURE_2D, tex_id);
+  /* Now load the image in this ideally unsupported format. Maybe
+   * things fail already here. Usually they don't. */
+  glTexImage2D (GL_TEXTURE_2D, 0, GL_RGB16,
+                width, height,
+                0, GL_RGB, GL_UNSIGNED_SHORT, g_bytes_get_data (bytes, NULL));
+  g_bytes_unref (bytes);
+  /* Generate mipmaps. GLES should give up now.
+   * GL should turn the checkerboard into orange mipmap levels though.
+   */
+  glGenerateMipmap (GL_TEXTURE_2D);
+
+  glGenFramebuffers (1, &fb_id);
+  glBindFramebuffer (GL_READ_FRAMEBUFFER, fb_id);
+  /* Bind mipmap level 2 for reading, so we rely on properly converted
+   * mipmaps. */
+  glFramebufferTexture2D (GL_READ_FRAMEBUFFER, GL_COLOR_ATTACHMENT0, GL_TEXTURE_2D, tex_id, 2);
+
+  /* On GLES, this should now fail due to incomplete framebuffer and
+   * leave us with the green contents we've drawn above.
+   * Or we are on GL, everything works perfectly, and we now get orange. */
+  glBlitFramebuffer (0, 0,
+                     width / 4, height / 4,
+                     0, 0,
+                     gtk_widget_get_width (glarea) * gtk_widget_get_scale_factor (glarea),
+                     gtk_widget_get_height (glarea) * gtk_widget_get_scale_factor (glarea),
+                     GL_COLOR_BUFFER_BIT,
+                     GL_LINEAR);
+
+  glDeleteFramebuffers (1, &fb_id);
+  glDeleteTextures (1, &tex_id);
+
+  return TRUE;
+}
+

testsuite/reftests/glarea-gl-only.css

@@ -0,0 +1,6 @@
+.orange {
+  /* The color of the mipmap'ed image */
+  background-color: #ff7000;
+  /* So the error label doesn't show */
+  color: transparent;
+}

testsuite/reftests/glarea-gl-only.ref.ui

@@ -0,0 +1,11 @@
+<?xml version="1.0" encoding="UTF-8"?>
+<interface>
+  <object class="GtkWindow" id="window1">
+    <property name="width_request">32</property>
+    <property name="height_request">32</property>
+    <property name="decorated">0</property>
+    <style>
+      <class name="orange"/>
+    </style>
+  </object>
+</interface>

testsuite/reftests/glarea-gl-only.ui

@@ -0,0 +1,17 @@
+<?xml version="1.0" encoding="UTF-8"?>
+<interface>
+  <object class="GtkWindow" id="window1">
+    <property name="width_request">32</property>
+    <property name="height_request">32</property>
+    <property name="decorated">0</property>
+    <child>
+      <object class="GtkGLArea">
+        <property name="allowed-apis">gl</property>
+        <signal name="render" handler="reftest:render_orange_glonly" swapped="no"/>
+        <style>
+          <class name="orange"/>
+        </style>
+      </object>
+    </child>
+  </object>
+</interface>

testsuite/reftests/meson.build

@@ -18,6 +18,7 @@ libreftest = library('reftest',
   sources: [
     'expand-expander.c',
     'frame-inhibitor.c',
+    'glarea-gl-only.c',
     'letter-spacing.c',
     'set-default-direction.c',
     'statusbar-remove-all.c',
@@ -308,6 +309,9 @@ testdata = [
   'font-sizes-names.css',
   'font-sizes-names.ref.ui',
   'font-sizes-names.ui',
+  'glarea-gl-only.css',
+  'glarea-gl-only.ref.ui',
+  'glarea-gl-only.ui',
   'gtk-image-effect-inherit.css',
   'gtk-image-effect-inherit.ref.ui',
   'gtk-image-effect-inherit.ui',