From 461ce87b52eb16acf6e48c87cfe574f89f86bdfd Mon Sep 17 00:00:00 2001
From: Alexander Larsson <alexl@redhat.com>
Date: Mon, 21 Sep 2020 15:14:40 +0200
Subject: [PATCH] gl backend: Add line numbers to source in glsl compilation
 errors

Almost always the source is created by combining various sources, which
means the line numbers in the error messages are hard to use. Adding
the line numbers to the source in the error message helps with this.
---
 gsk/gl/gskglshaderbuilder.c | 24 ++++++++++++++++++++++--
 1 file changed, 22 insertions(+), 2 deletions(-)

diff --git a/gsk/gl/gskglshaderbuilder.c b/gsk/gl/gskglshaderbuilder.c
index b23c81a9b1..c0e763a85e 100644
--- a/gsk/gl/gskglshaderbuilder.c
+++ b/gsk/gl/gskglshaderbuilder.c
@@ -47,7 +47,9 @@ check_shader_error (int     shader_id,
   int log_len;
   char *buffer;
   int code_len;
-  char *code;
+  int line;
+  char *code, *p;
+  GString *s;
 
   glGetShaderiv (shader_id, GL_COMPILE_STATUS, &status);
 
@@ -62,11 +64,29 @@ check_shader_error (int     shader_id,
   code = g_malloc0 (code_len + 1);
   glGetShaderSource (shader_id, code_len, NULL, code);
 
+  s = g_string_new ("");
+  p = code;
+  line = 1;
+  while (*p)
+    {
+      char *end = strchr (p, '\n');
+      if (end)
+        end = end + 1; /* Include newline */
+      else
+        end = p + strlen (p);
+
+      g_string_append_printf (s, "%3d| ", line++);
+      g_string_append_len (s, p, end - p);
+
+      p = end;
+    }
+
   g_set_error (error, GDK_GL_ERROR, GDK_GL_ERROR_COMPILATION_FAILED,
                "Compilation failure in shader.\nError message: %s\n\nSource code:\n%s\n\n",
                buffer,
-               code);
+               s->str);
 
+  g_string_free (s, TRUE);
   g_free (buffer);
   g_free (code);