Bug 1531196 - Add a "small-screen" debug pref to shrink the overlay a bit. r=gw

Adaptive sizing would be better, but this is the simplest path to
victory.

Differential Revision: https://phabricator.services.mozilla.com/D21757

--HG--
extra : moz-landing-system : lando

gfx/thebes/gfxPlatform.cpp

@@ -566,6 +566,9 @@ static void WebRenderDebugPrefChangeCallback(const char* aPrefName, void*) {
   GFX_WEBRENDER_DEBUG(".picture-caching", 1 << 15)
   GFX_WEBRENDER_DEBUG(".texture-cache.disable-shrink", 1 << 16)
   GFX_WEBRENDER_DEBUG(".primitives", 1 << 17)
+  // Bit 18 is for the zoom display, which requires the mouse position and thus
+  // currently only works in wrench.
+  GFX_WEBRENDER_DEBUG(".small-screen", 1 << 19)
 #undef GFX_WEBRENDER_DEBUG
 
   gfx::gfxVars::SetWebRenderDebugFlags(flags);

gfx/wr/webrender/src/debug_render.rs

@@ -313,6 +313,7 @@ impl DebugRenderer {
         &mut self,
         device: &mut Device,
         viewport_size: Option<FramebufferIntSize>,
+        scale: f32,
     ) {
         if let Some(viewport_size) = viewport_size {
             device.disable_depth();
@@ -321,8 +322,8 @@ impl DebugRenderer {
 
             let projection = Transform3D::ortho(
                 0.0,
-                viewport_size.width as f32,
+                viewport_size.width as f32 * scale,
-                viewport_size.height as f32,
+                viewport_size.height as f32 * scale,
                 0.0,
                 ORTHO_NEAR_PLANE,
                 ORTHO_FAR_PLANE,

gfx/wr/webrender/src/renderer.rs

@@ -2782,7 +2782,9 @@ impl Renderer {
             let _gm = self.gpu_profile.start_marker("end frame");
             self.gpu_profile.end_frame();
             if let Some(debug_renderer) = self.debug.try_get_mut() {
-                debug_renderer.render(&mut self.device, framebuffer_size);
+                let small_screen = self.debug_flags.contains(DebugFlags::SMALL_SCREEN);
+                let scale = if small_screen { 1.6 } else { 1.0 };
+                debug_renderer.render(&mut self.device, framebuffer_size, scale);
             }
             // See comment for texture_resolver.begin_frame() for explanation
             // of why this must be done after all rendering, including debug

gfx/wr/webrender_api/src/api.rs

@@ -1040,6 +1040,10 @@ bitflags! {
         const PRIMITIVE_DBG = 1 << 17;
         /// Draw a zoom widget showing part of the framebuffer zoomed in.
         const ZOOM_DBG = 1 << 18;
+        /// Scale the debug renderer down for a smaller screen. This will disrupt
+        /// any mapping between debug display items and page content, so shouldn't
+        /// be used with overlays like the picture caching or primitive display.
+        const SMALL_SCREEN = 1 << 19;
     }
 }
 

modules/libpref/init/all.js

@@ -965,6 +965,7 @@ pref("gfx.webrender.debug.show-overdraw", false);
 pref("gfx.webrender.debug.slow-frame-indicator", false);
 pref("gfx.webrender.debug.picture-caching", false);
 pref("gfx.webrender.debug.primitives", false);
+pref("gfx.webrender.debug.small-screen", false);
 pref("gfx.webrender.dl.dump-parent", false);
 pref("gfx.webrender.dl.dump-content", false);
 pref("gfx.webrender.picture-caching", true);