Evas GL: Fallback to safe values of depth, stencil & msaa if not supported

Depth32, Stencil16 and MSAA are known to be unsupported on many platforms.
While applications should try not to request them, we can try to fallback
nicely and still render using depth24+stencil8 (which is often supported),
or reducing the number of MSAA samples (until 0 if not supported at all).

diff --git a/src/modules/evas/engines/gl_x11/evas_x_main.c b/src/modules/evas/engines/gl_x11/evas_x_main.c
index fccf47d..b192d60 100644 (file)
--- a/src/modules/evas/engines/gl_x11/evas_x_main.c
+++ b/src/modules/evas/engines/gl_x11/evas_x_main.c
@@ -784,7 +784,11 @@ eng_best_visual_get(Evas_Engine_Info_GL_X11 *einfo)
              int config_attrs[40], i, n, num;
              int depth = DefaultDepth(einfo->info.display,
                                       einfo->info.screen);
+             int depth_bits = einfo->depth_bits;
+             int stencil_bits = einfo->stencil_bits;
+             int msaa_samples = einfo->msaa_bits;
 
+try_again:
              n = 0;
              config_attrs[n++] = EGL_SURFACE_TYPE;
              config_attrs[n++] = EGL_WINDOW_BIT;
@@ -814,31 +818,55 @@ eng_best_visual_get(Evas_Engine_Info_GL_X11 *einfo)
                   config_attrs[n++] = 0;
                }
 
-             if (einfo->depth_bits)
+             if (depth_bits)
                {
                   config_attrs[n++] = EGL_DEPTH_SIZE;
-                  config_attrs[n++] = einfo->depth_bits;
+                  config_attrs[n++] = depth_bits;
                }
 
-             if (einfo->stencil_bits)
+             if (stencil_bits)
                {
                   config_attrs[n++] = EGL_STENCIL_SIZE;
-                  config_attrs[n++] = einfo->stencil_bits;
+                  config_attrs[n++] = stencil_bits;
                }
 
-             if (einfo->msaa_bits)
+             if (msaa_samples)
                {
                   config_attrs[n++] = EGL_SAMPLE_BUFFERS;
                   config_attrs[n++] = 1;
                   config_attrs[n++] = EGL_SAMPLES;
-                  config_attrs[n++] = einfo->msaa_bits;
+                  config_attrs[n++] = msaa_samples;
                }
              config_attrs[n++] = EGL_NONE;
              num = 0;
              if ((!eglChooseConfig(egl_disp, config_attrs, configs, 200, &num))
                  || (num < 1))
                {
-                  ERR("eglChooseConfig() can't find any configs");
+                  ERR("eglChooseConfig() can't find any configs (gles%d, alpha: %d, depth: %d, stencil: %d, msaa: %d)",
+                      gles3_supported ? 3 : 2, alpha, depth_bits, stencil_bits, msaa_samples);
+                  if ((depth_bits > 24) || (stencil_bits > 8))
+                    {
+                       WRN("Please note that GLES might not support 32-bit depth or "
+                           "16-bit stencil buffers, so depth24, stencil8 are the maximum "
+                           "recommended values.");
+                       if (depth_bits > 24) depth_bits = 24;
+                       if (stencil_bits > 8) stencil_bits = 8;
+                       DBG("Trying again with depth:%d, stencil:%d", depth_bits, stencil_bits);
+                       goto try_again;
+                    }
+                  else if (msaa_samples)
+                    {
+                       msaa_samples /= 2;
+                       DBG("Trying again with msaa_samples: %d", msaa_samples);
+                       goto try_again;
+                    }
+                  else if (depth_bits || stencil_bits)
+                    {
+                       depth_bits = 0;
+                       stencil_bits = 0;
+                       DBG("Trying again without any depth or stencil buffer");
+                       goto try_again;
+                    }
                   return NULL;
                }
              found = EINA_FALSE;
@@ -973,6 +1001,7 @@ eng_best_visual_get(Evas_Engine_Info_GL_X11 *einfo)
                   config_attrs[i++] = GLX_ALPHA_SIZE;
                   config_attrs[i++] = 0;
                }
+             // TODO: Implement support for depth, stencil & msaa
              config_attrs[i++] = GLX_DEPTH_SIZE;
              config_attrs[i++] = 0;
              config_attrs[i++] = GLX_STENCIL_SIZE;