Fix app unresponsive when loading images

[isaac-weisberg]

Right now there are several cases in the launcher where the app becomes unresponsive:

• selecting a server
• opening Media page for the first time
• opening Results page for the first time
• randomly when scrolling around in the cars list

I have profiled the application in Visual Studio, and I have found out that most of the CPU time of the program has been taken by BetterImage.cs calling BitmapImage.EndInit()

BetterImage.cs tries to decode images less than 50 KB synchronously on the UI thread, however what happens is that BitmapImage.EndInit() underneath calls FinalizeCreation(), which inside has logic that causes the color profile of the source image to be converted via a call to new ColorConvertedBitmap which under the hood calls UnsafeNativeMethods.WICColorTransform.Initialize, which is implemented by a blocking interop service call. This procedure ends up being very slow, and because it's on main thread, this causes UI to stutter.

My proposed solution is to reduce altogether the work needed by disabling the color profile conversion via providing CreateOptions = BitmapCreateOptions.IgnoreColorProfile.

This has caused some images to cause an exception in the BetterImage.cs automatic cropping functionality available via DependencyProperty CropTransparentAreas. There was an invalid assumption of what the characteristics of an image were supposed to be in order to fit into a fixed size array. I have fixed it by checking directly against the size of the buffer rather than the width and stride values.

After the fix, the navigation in the app is instantaneous, there is no more unresponsiveness. Profiling after the fix shows drastic fall in CPU usage and the Hot Path is now nothing significant.

Before the fix:

After the fix:

Video:

Before:

before.720.mov

After:

after.720.mov