The Height Units variable controls how a unit is vertically sized, which may be relative to its parent. By default an object uses Absolute height, where each unit represents 1 pixel of height in pixels. When using Absolute, an object ignores its parents' Width.
The following shows a child ColoredRectangle with 50 Absolute Height:
The following shows a child ColoredRectangle with -10 Relative to Container Height, which means is sized 10 pixels less tall than its parent.
Despite the name referring to a "Container", the size is relative to the parent regardless of the parent's type. If the instance has no parent, then the size is relative to the canvas.
The following shows a child ColoredRectangle with 100 Percentage Height, which means it has 100% of the height of its parent. Note that 100 Percentage is the same as 0 Relative to Container:
Despite the name referring to a "Container", the size is relative to the parent regardless of the parent's type. If the instance has no parent, then the size is relative to the canvas.
Ratio of Container can be used to fill available space or to share available space with other objects using a ratio.
Despite the name referring to a "Container", the total size available for ratios is relative to the parent regardless of the parent's type. If the instance has no parent, then the size is relative to the canvas.
The simplest case is a single child in a container with its Height Units set to Ratio of Container.
In this case the blue ColoredRectangle has no siblings (its container has no other children), so it occupies the entire parent height. If a second child is added (by copy/pasting the existing child), then each child is given 1 ratio value, which means each is 1/2 of the size of the entire parent.
To better visualize the effect of ratio, it's common to set the parent's Children Layout to Top to Bottom Stack, and to give each child a different color as shown in the following image.
As more children are added, each child's height is adjusted to make room for the new children.
Ratio values are distributed among all siblings using Ratio of Container proportionally. The image above shows four siblings, each given 1/4 of the ratio. If one of the the ratios changes (such as by increasing the second sibling's Height value to 3), then all siblings adjust in response to this change.
In this case, the total ratio is 6 (1 + 3 + 1 + 1), so the red is given 3/6 (1/2) of the container's height, while each of the others is given 1/6 of the container's height.
Values of 0 are supported, resulting in the object drawing with an absolute height of 0.
Ratio of Container is calculated after accounting for the height of children which are using absolute height. For example, if the height of the first child is 80 with a Height Units of Absolute, then the other three shrink to give the first the necessary room.
This effect can also be seen by adjusting the height using the handles.
Gum ignores invisible objects when calculating available space for Ratio Width units. Therefore, if a sibling is invisible, Gum treats it as if it has 0 height which allows all other Ratio siblings to expand.
Ratio of Container also respects Stack Spacing. A Stack Spacing value greater than 0 removes the available space for all children with a Height Units of Relative to Container.
The following image shows a child ColoredRectangle with 50 RelativeToChildren Height, which means that it is 50 pixels taller than is necessary to contain its children. Since the rectangle has no children, this is the same as having 50 Absolute Height:
RelativeToChildren can be used to size an object based on the position and sizes of a container's children. The following image shows a container with 0 RelativeToChildren Height, which mans that its height is set just large enough to contain its children. Notice that if the children are moved, the rectangle's height adjusts. Both children are considered so the container adjusts its height according to the bottom-most side of either child:
A non-zero Height when using RelativeToChildren can be used to add additional padding to a parent container. The following shows how changing the height can adjust the absolute height relative to children:
If a parent sets its Height Units to Relative to Children, then it must resize itself to contain its children. Normally, the height of the entire parent is determined by the child which needs the most space vertically. If the parent uses an Auto Grid Vertical layout, then the children control the size of the cells rather than the entire parent. Since all cells must be the same size, the child which needs the most amount of space vertically determines the height of all cells.
For example, the following image shows a four by four grid, each containing one white rectangle. The first rectangle has an absolute width and height of 100, so each cell is sized to be 100x100. Note that the other rectangles are 50x50.
The largest child determines the cell size for all other children. Therefore, if a child is moved or resized so it outgrows its cell, then the parent height adjusts in response.
The term "children" can refer to:
Instances added to a parent, such as ColoredRectangles added to a Container
Individual letters in a Text instance - each letter and line of text can expand the height of its parent
The following animation shows a Text instance which has its Height Units set to RelativeToChildren. As more lines of text are added, the Text automatically expands in size.
The height of a Text instance using Relative to Children depends on the number of lines displayed by the Text instance and the maximum line height given the current font properties. Therefore, the height of a Text stance remains the same regardless of the contents of a single line.
For example, the following image contains multiple Text instances. Each has a single line of text, but the line of text differs in the height of each character. Notice that the texts are all the same height even though the contents of their lines differ.
Percentage of Other Dimension adjusts the object's effective height so it remains proportional to the Width value multiplied by the Height value (as a percentage). For example, if a Height value of 200 is entered, then the effective height is 200% (2x) of the width.
The following image shows a child ColoredRectangle with a Height of 200 Percentage of Other Dimension. In this image, the Width value is 50 units, so the effective height is 100 units:
The Sprite type has an extra Height Unit called Percentage of Source File, which sets the height of the Sprite according to the file that it is displaying. This is the default Height Unit for Sprites.
The following image shows a child Sprite with 200 Percentage of Source File Height, which means it draws two times as tall as its source image:
