private void ResetImage()
{
if (!HasImage)
{
return;
}
_surface.Background = null;
if (_brush != null)
{
_brush.ImageSource = null;
_brush = null;
}
if (_source != null)
{
_source.ClearResources();
_source = null;
}
HasImage = false;
}
private async void ShowImage()
{
if (!CanLoad || !HasAppliedTemplate || !IsLoaded || HasImage)
{
return;
}
ResetImage();
if (UriSource == null)
{
return;
}
SetProgress(0);
VisualStateManager.GoToState(this, "Unloaded", true);
// For thread safety, save current value of UriSource
var uriSource = UriSource;
HasImage = true;
using (var stream = await GetImageStreamAsync(uriSource)) // This is not thread-safe!
{
// Technically, at each await exists the possibility that UriSource can be changed.
// We need to ensure that this hasn't happened, otherwise we run the risk of leaking resources
// or doing other bad things.
if (uriSource != UriSource)
{
return;
}
if (stream == null)
{
VisualStateManager.GoToState(this, "Failed", true);
return;
}
try
{
var decoder = await BitmapDecoder.CreateAsync(stream);
var source = new GifImageSource((int)decoder.PixelWidth, (int)decoder.PixelHeight)
{
EnablePrerender = true
};
await source.SetSourceAsync(stream);
// It's possible that the URI changed, or the control has been unloaded, etc. If so,
// clear resources and quit.
if (uriSource != UriSource || !IsLoaded || !CanLoad)
{
// Clean up GifImageSource and return
source.ClearResources();
return;
}
// Must wait for async operations to complete before setting _source
_source = source;
}
catch (Exception)
{
VisualStateManager.GoToState(this, "Failed", true);
return;
}
}
_brush = new ImageBrush {
ImageSource = _source, Stretch = Stretch.None
};
_surface.Background = _brush;
_surface.Height = _source.Height;
_surface.Width = _source.Width;
// Render one frame so that we show something even if the gif is paused
_source.RenderFrame();
VisualStateManager.GoToState(this, "Loaded", true);
CheckTimer();
_fireImageOpened = true;
}