From 372b9c4edd42b67827b75863b978091ba5cff5cd Mon Sep 17 00:00:00 2001
From: Marius Vlad <marius.vlad@collabora.com>
Date: Thu, 17 Oct 2024 17:25:41 +0300
Subject: [PATCH 1/2] backend/wayland_egl: Add a fallback eglConfig

This seems to aid flutter-auto at displaying an image on agl-rdp
with software rendering, and on agl-kvm with virgl.  Makes uses of a fallback
eGLConfig (< 24 bit) and tries to use that one rather than the default one (24-bit).

Bug-AGL: SPEC-5260
Signed-off-by: Marius Vlad <marius.vlad@collabora.com>
---
 cmake/config_common.h.in         | 17 ++++++++++++++++-
 shell/backend/wayland_egl/egl.cc | 23 ++++++++++++++++++++---
 2 files changed, 36 insertions(+), 4 deletions(-)

diff --git a/cmake/config_common.h.in b/cmake/config_common.h.in
index 07ce9b7..2c54c67 100644
--- a/cmake/config_common.h.in
+++ b/cmake/config_common.h.in
@@ -155,6 +155,21 @@ static constexpr std::array<EGLint, 27> kEglConfigAttribs = {{
     // clang-format on
 }};
 
+
+static constexpr std::array<EGLint, 27> kEglConfigAttribsFallBack = {{
+    // clang-format off
+    EGL_SURFACE_TYPE, EGL_WINDOW_BIT,
+    EGL_RENDERABLE_TYPE, EGL_OPENGL_ES2_BIT,
+
+    EGL_RED_SIZE, 1,
+    EGL_GREEN_SIZE, 1,
+    EGL_BLUE_SIZE, 1,
+    EGL_ALPHA_SIZE, 2,
+    EGL_NONE // termination sentinel
+    // clang-format on
+}};
+
+
 // All vkCreate* functions take an optional allocator. For now, we select the
 // default allocator by passing in a null pointer, and we highlight the argument
 // by using the VKALLOC constant.
@@ -181,4 +196,4 @@ constexpr struct VkAllocationCallbacks* VKALLOC = nullptr;
 #cmakedefine01 ENV32BIT
 #cmakedefine01 ENV64BIT
 
-#endif //CONFIG_COMMON_H_
\ No newline at end of file
+#endif //CONFIG_COMMON_H_
diff --git a/shell/backend/wayland_egl/egl.cc b/shell/backend/wayland_egl/egl.cc
index 99555d6..70164ba 100644
--- a/shell/backend/wayland_egl/egl.cc
+++ b/shell/backend/wayland_egl/egl.cc
@@ -62,11 +62,28 @@ Egl::Egl(void* native_display, int buffer_size, bool debug)
       break;
     }
   }
-  free(configs);
   if (m_config == nullptr) {
-    spdlog::critical("did not find config with buffer size {}", m_buffer_size);
-    assert(false);
+    // try with the fallback one
+    spdlog::critical("Could not use default EGLConfig trying with fallback.");
+    ret = eglChooseConfig(m_dpy, kEglConfigAttribsFallBack.data(), configs,
+                          count, &n);
+    assert(ret && n >= 1);
+
+    for (EGLint i = 0; i < n; i++) {
+      eglGetConfigAttrib(m_dpy, configs[i], EGL_BUFFER_SIZE, &size);
+      SPDLOG_DEBUG("Buffer size for config {} is {}", i, size);
+      if (m_buffer_size <= size) {
+        memcpy(&m_config, &configs[i], sizeof(EGLConfig));
+        break;
+      }
+    }
+    if (m_config == nullptr) {
+      spdlog::critical("did not find config with buffer size {}",
+                       m_buffer_size);
+      assert(false);
+    }
   }
+  free(configs);
 
   m_context = eglCreateContext(m_dpy, m_config, EGL_NO_CONTEXT,
                                kEglContextAttribs.data());
-- 
2.43.0