gl-renderer: dump failed shader source

To help debugging shader compilation errors, print the shader source the
way it was given to the GLSL compiler and with line numbers that match
the compiler error messages.

This is necessary because some snippets are added at runtime to the
beginning, the source is not only what is in the respective .glsl file.

I did look into using #line directives, but you cannot put source file
names to it, only "source string numbers" which must be an integer
expression. If we used #line, the reader would need to know that string
number 0 is the version, string 1 is the config and string number 2 is
fragment.glsl. I think that would have been too cumbersome.

Signed-off-by: Pekka Paalanen <pekka.paalanen@collabora.com>

libweston/renderer-gl/gl-shaders.c

@@ -29,6 +29,8 @@
 
 #include <GLES2/gl2.h>
 
+#include <string.h>
+
 #include "gl-renderer.h"
 #include "gl-renderer-internal.h"
 
@@ -38,6 +40,43 @@
 /* static const char fragment_shader[]; fragment.glsl */
 #include "fragment-shader.h"
 
+static void
+dump_program_with_line_numbers(int count, const char **sources)
+{
+	FILE *fp;
+	char *dumpstr;
+	size_t dumpstrsz;
+	const char *cur;
+	const char *delim;
+	int line = 1;
+	int i;
+	bool new_line = true;
+
+	fp = open_memstream(&dumpstr, &dumpstrsz);
+	if (!fp)
+		return;
+
+	for (i = 0; i < count; i++) {
+		cur = sources[i];
+		while ((delim = strchr(cur, '\n'))) {
+			if (new_line)
+				fprintf(fp, "%6d: ", line++);
+			fprintf(fp, "%.*s\n", (int)(delim - cur), cur);
+			new_line = true;
+			cur = delim + 1;
+		}
+		if (new_line)
+			fprintf(fp, "%6d: ", line++);
+		new_line = false;
+		fprintf(fp, "%s", cur);
+	}
+
+	if (fclose(fp) == 0)
+		weston_log_continue("%s\n", dumpstr);
+
+	free(dumpstr);
+}
+
 static int
 compile_shader(GLenum type, int count, const char **sources)
 {
@@ -52,6 +91,8 @@ compile_shader(GLenum type, int count, const char **sources)
 	if (!status) {
 		glGetShaderInfoLog(s, sizeof msg, NULL, msg);
 		weston_log("shader info: %s\n", msg);
+		weston_log("shader source:\n");
+		dump_program_with_line_numbers(count, sources);
 		return GL_NONE;
 	}