Delay display configuration after waking up from suspend with multi displays

ui/display/chromeos/display_configurator.cc

Index: ui/display/chromeos/display_configurator.cc
diff --git a/ui/display/chromeos/display_configurator.cc b/ui/display/chromeos/display_configurator.cc
index 6c3062317944388f13615d2e7ae7d6db5a276a5a..56bd10da733baee5d26345555444dcc9617ed11a 100644
--- a/ui/display/chromeos/display_configurator.cc
+++ b/ui/display/chromeos/display_configurator.cc
@@ -31,10 +31,6 @@ namespace {
 
 typedef std::vector<const DisplayMode*> DisplayModeList;
 
-// The delay to perform configuration after RRNotify. See the comment for
-// |configure_timer_|.
-const int kConfigureDelayMs = 500;
-
 // The EDID specification marks the top bit of the manufacturer id as reserved.
 const int16_t kReservedManufacturerID = static_cast<int16_t>(1 << 15);
 
@@ -862,6 +858,14 @@ void DisplayConfigurator::SetDisplayPowerInternal(
   pending_power_flags_ = flags;
   queued_configuration_callbacks_.push_back(callback);
 
+  if (configure_timer_.IsRunning()) {
+    // If there is a configuration task scheduled, avoid performing
+    // configuration immediately. Instead reset the timer to wait for things to
+    // settle.
+    configure_timer_.Reset();
+    return;
+  }
+
   RunPendingConfiguration();
 }
 
@@ -916,13 +920,11 @@ void DisplayConfigurator::OnConfigurationChanged() {
 
   // Configure displays with |kConfigureDelayMs| delay,
   // so that time-consuming ConfigureDisplays() won't be called multiple times.
-  if (configure_timer_.IsRunning()) {
-    // Note: when the timer is running it is possible that a different task
-    // (RestoreRequestedPowerStateAfterResume()) is scheduled. In these cases,
-    // prefer the already scheduled task to ConfigureDisplays() since
-    // ConfigureDisplays() performs only basic configuration while
-    // RestoreRequestedPowerStateAfterResume() will perform additional
-    // operations.
+  if (configure_timer_.IsRunning() &&
+      configure_timer_.GetCurrentDelay() <=
+          base::TimeDelta::FromMilliseconds(kConfigureDelayMs)) {
+    // Avoid resetting the timer to a huge delay if we are currently pending
+    // the delayed configuration after waking up from suspend.
     configure_timer_.Reset();
   } else {
     configure_timer_.Start(
@@ -967,15 +969,7 @@ void DisplayConfigurator::SuspendDisplays(
 }
 
 void DisplayConfigurator::ResumeDisplays() {
-  if (!configure_display_ || display_externally_controlled_)
-    return;
-
-  displays_suspended_ = false;
-
-  // If requested_power_state_ is ALL_OFF due to idle suspend, powerd will turn
-  // the display power on when it enables the backlight.
-  SetDisplayPower(requested_power_state_, kSetDisplayPowerNoFlags,
-                  base::Bind(&DoNothing));
+  ResumeDisplaysInternal(base::Bind(&DoNothing));

[Daniel Erat, 2016/10/21 21:09:44]

this seems weird: a helper method that's only called in one place? why isn't the
code directly in this method?

[afakhry, 2016/10/22 00:28:48]

Unittests need to provide a callback, but clients of the DisplayConfigurator
don't care whether configuration was done or not.

 }
 
 void DisplayConfigurator::ConfigureDisplays() {
@@ -1165,4 +1159,31 @@ bool DisplayConfigurator::IsDisplayOn() const {
   return current_power_state_ != chromeos::DISPLAY_POWER_ALL_OFF;
 }
 
+void DisplayConfigurator::ResumeDisplaysInternal(
+    const ConfigurationCallback& callback) {
+  if (!configure_display_ || display_externally_controlled_)
+    return;
+
+  displays_suspended_ = false;
+
+  // If requested_power_state_ is ALL_OFF due to idle suspend, powerd will turn
+  // the display power on when it enables the backlight.

[Daniel Erat, 2016/10/21 21:09:44]

did you mean to keep this comment above the SetDisplayPower call? it doesn't
seem to make much sense here.

[afakhry, 2016/10/22 00:28:48]

Yep, thanks for catching that. Done.

+  if (current_display_state_ == MULTIPLE_DISPLAY_STATE_DUAL_MIRROR ||
+      current_display_state_ == MULTIPLE_DISPLAY_STATE_DUAL_EXTENDED ||
+      current_display_state_ == MULTIPLE_DISPLAY_STATE_MULTI_EXTENDED) {
+    // When waking up from suspend while being in a multi display mode, we
+    // schedule a delayed forced configuration, which will make
+    // SetDisplayPowerInternal() avoid performing the configuration immediately.
+    // This gives a chance to wait for all displays to be added and detected
+    // before configuration is performed.
+    configure_timer_.Start(FROM_HERE,
+                           base::TimeDelta::FromMilliseconds(
+                               kResumeConfigureMultiDisplayDelayMs),
+                           this,
+                           &DisplayConfigurator::ConfigureDisplays);
+  }
+
+  SetDisplayPower(requested_power_state_, kSetDisplayPowerNoFlags, callback);
+}
+
 }  // namespace ui