From dfc7b59909588985ee1be19f313f8bfb858ab8b0 Mon Sep 17 00:00:00 2001
From: Niklas Haas <git@nand.wakku.to>
Date: Thu, 12 May 2016 11:27:00 +0200
Subject: vo_opengl: make the screen blue on shader errors

This helps visually signify that somthing went wrong, and prevents
confusing shader compilation errors with other types of bugs.
---
 video/out/opengl/utils.c | 18 ++++++++++++++++++
 video/out/opengl/utils.h |  2 ++
 video/out/opengl/video.c | 11 +++++++++++
 3 files changed, 31 insertions(+)

diff --git a/video/out/opengl/utils.c b/video/out/opengl/utils.c
index d29d7b0bdb..5ef99ac599 100644
--- a/video/out/opengl/utils.c
+++ b/video/out/opengl/utils.c
@@ -485,6 +485,8 @@ struct gl_shader_cache {
     struct sc_uniform uniforms[SC_UNIFORM_ENTRIES];
     int num_uniforms;
 
+    bool error_state; // true if an error occurred
+
     // temporary buffers (avoids frequent reallocations)
     bstr tmp[5];
 };
@@ -532,6 +534,16 @@ void gl_sc_destroy(struct gl_shader_cache *sc)
     talloc_free(sc);
 }
 
+bool gl_sc_error_state(struct gl_shader_cache *sc)
+{
+    return sc->error_state;
+}
+
+void gl_sc_reset_error(struct gl_shader_cache *sc)
+{
+    sc->error_state = false;
+}
+
 void gl_sc_enable_extension(struct gl_shader_cache *sc, char *name)
 {
     bstr_xappend_asprintf(sc, &sc->prelude_text, "#extension %s : enable\n", name);
@@ -810,6 +822,9 @@ static void compile_attach_shader(struct gl_shader_cache *sc, GLuint program,
 
     gl->AttachShader(program, shader);
     gl->DeleteShader(shader);
+
+    if (!status)
+        sc->error_state = true;
 }
 
 static void link_shader(struct gl_shader_cache *sc, GLuint program)
@@ -828,6 +843,9 @@ static void link_shader(struct gl_shader_cache *sc, GLuint program)
         MP_MSG(sc, pri, "shader link log (status=%d): %s\n", status, logstr);
         talloc_free(logstr);
     }
+
+    if (!status)
+        sc->error_state = true;
 }
 
 static GLuint create_program(struct gl_shader_cache *sc, const char *vertex,
diff --git a/video/out/opengl/utils.h b/video/out/opengl/utils.h
index cec5a4b8e4..c7a72969f6 100644
--- a/video/out/opengl/utils.h
+++ b/video/out/opengl/utils.h
@@ -148,6 +148,8 @@ struct gl_shader_cache;
 
 struct gl_shader_cache *gl_sc_create(GL *gl, struct mp_log *log);
 void gl_sc_destroy(struct gl_shader_cache *sc);
+bool gl_sc_error_state(struct gl_shader_cache *sc);
+void gl_sc_reset_error(struct gl_shader_cache *sc);
 void gl_sc_add(struct gl_shader_cache *sc, const char *text);
 void gl_sc_addf(struct gl_shader_cache *sc, const char *textf, ...);
 void gl_sc_hadd(struct gl_shader_cache *sc, const char *text);
diff --git a/video/out/opengl/video.c b/video/out/opengl/video.c
index 2a1d623f0b..ae1800821f 100644
--- a/video/out/opengl/video.c
+++ b/video/out/opengl/video.c
@@ -613,6 +613,8 @@ static void uninit_rendering(struct gl_video *p)
 
     gl_video_reset_surfaces(p);
     gl_video_reset_hooks(p);
+
+    gl_sc_reset_error(p->sc);
 }
 
 void gl_video_update_profile(struct gl_video *p)
@@ -2500,6 +2502,8 @@ static void pass_render_frame(struct gl_video *p)
 
 static void pass_draw_to_screen(struct gl_video *p, int fbo)
 {
+    GL *gl = p->gl;
+
     if (p->dumb_mode)
         pass_render_frame_dumb(p, fbo);
 
@@ -2525,6 +2529,13 @@ static void pass_draw_to_screen(struct gl_video *p, int fbo)
 
     pass_dither(p);
     finish_pass_direct(p, fbo, p->vp_w, p->vp_h, &p->dst_rect);
+
+    if (gl_sc_error_state(p->sc)) {
+        // Make the screen solid blue to make it visually clear that an
+        // error has occurred
+        gl->ClearColor(0.0, 0.05, 0.5, 1.0);
+        gl->Clear(GL_COLOR_BUFFER_BIT);
+    }
 }
 
 // Draws an interpolate frame to fbo, based on the frame timing in t
-- 
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