Drag Gestures - fractional delta values

Question

I have an issue with objects moving roughly twice as far as expected when dragging them.

I am comparing my application to the standard TouchGestureSample sample from MSDN.

For some reason in my application gesture samples have fractional positions and deltas.

Both are using same Microsoft.Xna.Framework.Input.Touch.dll, v4.0.30319.

I am running both apps using standard Windows Phone Emulator.

I am setting my break point immediately after this line of code in a simple Update method:

GestureSample gesture = TouchPanel.ReadGesture();

Typical values in my app:

Delta = {X:-13.56522 Y:4.166667}
Position = {X:184.6956 Y:417.7083}

Typical values in sample app:

Delta = {X:7 Y:16}
Position = {X:497 Y:244}

Have anyone seen this issue? Does anyone have any suggestions?

Thank you.

Answer 1

Fractional values were caused by IsFullScreen set to false:

_graphics = new GraphicsDeviceManager(this)
                {
                    IsFullScreen = false, // Setting to true will make gesture deltas integer.
                    PreferredBackBufferWidth = 480,
                    PreferredBackBufferHeight = 800
                };

There is no visual difference between using fractional and integer values.

The bug with multiplied movement was caused by incorrect calculations inside my engine.