/// <summary>Service routine to paint the backing store bitmap for the map underlay.</summary>
protected virtual Bitmap PaintBuffer(Rectangle clipBounds)
{
if (DataContext.Model == null)
{
return(null);
}
Bitmap bitmap = null, temp = null;
try {
temp = ClientSize.AllocateBitmap();
using (var graphics = Graphics.FromImage(temp)) {
graphics.Clip = new Region(clipBounds);
graphics.Contain(PaintBuffer);
}
bitmap = temp;
temp = null;
} finally { if (temp != null)
{
temp.Dispose();
}
}
return(bitmap);
}
/// <inheritdoc/>
protected override async void OnPaint(PaintEventArgs e)
{
if (e == null)
{
throw new ArgumentNullException(nameof(e));
}
if (DesignMode)
{
e.Graphics.FillRectangle(Brushes.Gray, ClientRectangle); return;
}
if (IsMapDirty)
{
OnResize(EventArgs.Empty); IsMapDirty = false;
}
// TODO - Fix thread timing error work-around of catching and discarding InvalidOperationException.
if (_mapBuffer != null)
{
try { base.OnPaint(e); } catch (InvalidOperationException) { _count++; }
}
var status = Interlocked.CompareExchange(ref _cacheStatus, _IS_PAINTING, _NEEDS_PAINTING);
if (status == _NEEDS_PAINTING)
{
try {
if (_backBuffer != null)
{
_backBuffer.Dispose();
}
_backBuffer = Interlocked.Exchange(ref _mapBuffer, await PaintBufferAsync(ClientRectangle));
if (_backBuffer != null)
{
_backBuffer.Dispose();
}
_backBuffer = ClientSize.AllocateBitmap();
} catch (InvalidOperationException) {
if (_backBuffer == null)
{
_backBuffer = ClientSize.AllocateBitmap();
}
Interlocked.CompareExchange(ref _cacheStatus, _NEEDS_PAINTING, _IS_PAINTING);
Thread.Sleep(250);
} finally { Interlocked.CompareExchange(ref _cacheStatus, _IS_READY, _IS_PAINTING); }
Refresh();
}
IsUnitsDirty = false;
}