GumBatch

Introduction

GumBatch is an object which supports immediate mode rendering, similar to MonoGame's SpriteBatch. GumBatch can support rendering text with DrawString as well as any IRenderableIpso.

For information on getting your project set up to use GumBatch, see the Setup for GumBatch page.

Rendering Strings

GumBatch can be used to render strings directly. This requires a BitmapFont.

The following code renders a string at X = 100, Y=200:

gumBatch.Begin();
gumBatch.DrawString(
    font, 
    "I am at X=100, Y=200",
    new Vector2(100, 200), 
    Color.White);
gumBatch.End();

A single text object rendered using DrawString

Multiple strings can be rendered between Begin and End calls:

gumBatch.Begin();
for(int i = 0; i < 10; i++)
{
    gumBatch.DrawString(
        font, 
        $"This is string {i}", 
        new Vector2(0, 20*i), 
        Color.White);

}
gumBatch.End();

Multiple DrawString calls between Begin and End

DrawString can accept newlines and color the text:

gumBatch.Begin();
    gumBatch.DrawString(
        font, 
        $"This string contains\nnewlines which result in\nthe text rendering over multiple lines",
        new Vector2(20, 20), 
        Color.Purple);
gumBatch.End();

Colored text with newlines

Rendering TextRuntimes

If your text rendering requires more advanced positioning, wrapping, rotation, sizing, and so on, you can use TextRuntime instances.

TextRuntimes can be used in both GumBatch as well as they can be added to the SystemManagers if you use SystemManagers.Draw (retained mode).

The following code shows how to create a TextRuntime instance and render it using GumBatch:

// In Game1 at class scope:
TextRuntime textRuntime;

// In Initialize:
textRuntime = new TextRuntime();
textRuntime.UseCustomFont = true;
textRuntime.CustomFontFile = "Fonts/Font16Jing_Jing.fnt";
textRuntime.Text = 
    "I am an immediate mode TextRuntime. I am really long text which will wrap within the bounds of the TextRuntime";
textRuntime.X = 0;
textRuntime.XUnits = Gum.Converters.GeneralUnitType.PixelsFromMiddle;
textRuntime.XOrigin = HorizontalAlignment.Center;

textRuntime.Y = 0;
textRuntime.YUnits = Gum.Converters.GeneralUnitType.PixelsFromMiddle;
textRuntime.YOrigin = VerticalAlignment.Center;

textRuntime.HorizontalAlignment = HorizontalAlignment.Center;
textRuntime.VerticalAlignment = VerticalAlignment.Center;

textRuntime.Width = 300;
textRuntime.WidthUnits = Gum.DataTypes.DimensionUnitType.Absolute;
textRuntime.Height = 0;
textRuntime.HeightUnits = Gum.DataTypes.DimensionUnitType.RelativeToChildren;

textRuntime.Rotation = 90;

// In Draw:
gumBatch.Begin();
gumBatch.Draw(textRuntime);
gumBatch.End();

Rendering a TextRuntime in immediate mode with GumBatch

Rendering Parent/Child Hierarchy

GumBatch.Draw renders any argument renderable object. If the object has children, then the Draw call performs a hierarchical draw, respecting the parent/child relationship to control draw order.

For example, the following code creates a parent ColoredRectangleRuntime and a child TextRuntime:

Since the Draw call is only called on the Parent, then only the Parent reference is kept at class scope:

// at class scope:
ColoredRectangleRuntime buttonRectangle;

// in initialize:
// It's possible to create a runtime object...
buttonRectangle = new ColoredRectangleRuntime();
buttonRectangle.Width = 128;
buttonRectangle.Height = 32;
buttonRectangle.Color = Color.DarkBlue;
buttonRectangle.X = 0;
buttonRectangle.Y = 100;
// ... and add children to it:
var buttonText = new TextRuntime();
buttonText.Text = "Button text";
buttonText.X = 0;
buttonText.Y = 0;
buttonText.Width = 0;
buttonText.Height = 0;
buttonText.XUnits = Gum.Converters.GeneralUnitType.PixelsFromMiddle;
buttonText.YUnits = Gum.Converters.GeneralUnitType.PixelsFromMiddle;
buttonText.XOrigin = HorizontalAlignment.Center;
buttonText.YOrigin = VerticalAlignment.Center;
buttonText.HorizontalAlignment = HorizontalAlignment.Center;
buttonText.VerticalAlignment = VerticalAlignment.Center;
buttonText.WidthUnits = Gum.DataTypes.DimensionUnitType.RelativeToContainer;
buttonText.HeightUnits = Gum.DataTypes.DimensionUnitType.RelativeToContainer;
buttonRectangle.Children.Add(buttonText);

// Then draw call is only performed on the buttonRectangle - the children 
// (buttonText) are drawn automatically:
gumBatch.Begin();
gumBatch.Draw(buttonRectangle);
gumBatch.End();

buttonRectangle drawn with its child buttonText

RenderTargets

GumBatch can be used to render Gum objects on RenderTarget2Ds, just like regular SpriteBatch calls.

The following code shows how to render on a RenderTarget:

// Assuming MyRenderTarget is a valid render target:
GraphicsDevice.SetRenderTarget(MyRenderTarget);
gumBatch.Begin();
gumBatch.Draw(SomeGumObject);
gumBatch.End();

// now set the render target to null to draw it to screen:
GraphicsDevice.SetRenderTarget(null);
spriteBatch.Draw(MyRenderTarget, new Vector2(0, 0), Color.White);

Note that if you are rendering multiple objects on a render target, the BlendState must be set as to add the transparency. Using the default BlendState may result in alpha being "removed" from the render target when new instances are drawn.

The following shows how to create a BlendState for objects which have partial transpraency and are to be drawn on RenderTargets:

var blendState = new BlendState();

blendState.ColorSourceBlend = BlendState.NonPremultiplied.ColorSourceBlend;
blendState.ColorDestinationBlend = BlendState.NonPremultiplied.ColorDestinationBlend;
blendState.ColorBlendFunction = BlendState.NonPremultiplied.ColorBlendFunction;

blendState.AlphaSourceBlend = Blend.SourceAlpha;
blendState.AlphaDestinationBlend = Blend.DestinationAlpha;
blendState.AlphaBlendFunction = BlendFunction.Add;

halfTransparentRectangle.BlendState = blendState;