wined3d: Only use the LSB of the _SAMP_SRGB_TEXTURE state value.

dlls/wined3d/context.c

@@ -3719,7 +3719,7 @@ static void context_preload_texture(struct wined3d_context *context,
     if (!(texture = state->textures[idx]))
         return;
 
-    wined3d_texture_load(texture, context, state->sampler_states[idx][WINED3D_SAMP_SRGB_TEXTURE]);
+    wined3d_texture_load(texture, context, is_srgb_enabled(state->sampler_states[idx]));
 }
 
 /* Context activation is done by the caller. */

dlls/wined3d/state.c

@@ -3574,7 +3574,7 @@ static void wined3d_sampler_desc_from_sampler_states(struct wined3d_sampler_desc
         desc->max_anisotropy = 1;
     desc->compare = texture_gl->t.resource.format_flags & WINED3DFMT_FLAG_SHADOW;
     desc->comparison_func = WINED3D_CMP_LESSEQUAL;
-    desc->srgb_decode = sampler_states[WINED3D_SAMP_SRGB_TEXTURE];
+    desc->srgb_decode = is_srgb_enabled(sampler_states);
 
     if (!(texture_gl->t.resource.format_flags & WINED3DFMT_FLAG_FILTERING))
     {
@@ -3615,9 +3615,9 @@ static void sampler(struct wined3d_context *context, const struct wined3d_state
     if (state->textures[sampler_idx])
     {
         struct wined3d_texture_gl *texture_gl = wined3d_texture_gl(state->textures[sampler_idx]);
-        BOOL srgb = state->sampler_states[sampler_idx][WINED3D_SAMP_SRGB_TEXTURE];
         const DWORD *sampler_states = state->sampler_states[sampler_idx];
         struct wined3d_device *device = context->device;
+        BOOL srgb = is_srgb_enabled(sampler_states);
         struct wined3d_sampler_desc desc;
         struct wined3d_sampler *sampler;
         struct wine_rb_entry *entry;

dlls/wined3d/wined3d_private.h

@@ -4591,6 +4591,18 @@ static inline void context_apply_state(struct wined3d_context *context,
     state_table[rep].apply(context, state, rep);
 }
 
+static inline BOOL is_srgb_enabled(const DWORD *sampler_states)
+{
+    /* Only use the LSB of the WINED3D_SAMP_SRGB_TEXTURE value. This matches
+     * the behaviour of the AMD Windows driver.
+     *
+     * Might & Magic: Heroes VI - Shades of Darkness sets
+     * WINED3D_SAMP_SRGB_TEXTURE to a large value that looks like a
+     * pointer—presumably by accident—and expects sRGB decoding to be
+     * disabled. */
+    return sampler_states[WINED3D_SAMP_SRGB_TEXTURE] & 0x1;
+}
+
 static inline BOOL needs_separate_srgb_gl_texture(const struct wined3d_context *context,
         const struct wined3d_texture *texture)
 {