16 KiB
The Node file format
GSK render nodes can be serialized and deserialized using APIs such as gsk_render_node_serialize() and gsk_render_node_deserialize(). The intended use for this is development - primarily the development of GTK - by allowing things such as creating testsuites and benchmarks, exchanging nodes in bug reports. GTK includes the gtk4-node-editor application for creating such test files.
The format is a text format that follows the CSS syntax rules. In particular, this means that every array of bytes will produce a render node when parsed, as there is a defined error recovery method. For more details on error handling, please refer to the documentation of the parsing APIs.
The grammar of a node text representation using the CSS value definition syntax looks like this:
document: <node>\*
node: container [ "name" ] { } | <node-type> [ "name" ] { <property>* } | "name"
property: <property-name>: <node> | <value> ;
Each node has its own <node-type> and supports a custom set of properties, each with their own <property-name> and syntax. The following paragraphs document each of the nodes and their properties.
When serializing and the value of a property equals the default value, this value will not be serialized. Serialization aims to produce an output as small as possible.
To embed newlines in strings, use \A. To break a long string into multiple lines, escape the newline with a .
Names
Nodes
Nodes can be given a name by adding a string after the <node-type> in their definition. That same node can then be used further down in the document by specifying just the name identifying the node.
Textures
Just like nodes, textures can be referenced by name. When defining a named texture, the name has to be placed in front of the URL.
Nodes
container
The container node is a special node that allows specifying a list of child nodes. Its contents follow the same rules as an empty document.
blend
| property | syntax | default | printed |
|---|---|---|---|
| bottom | <node> |
color { } | always |
| mode | <blend-mode> |
normal | non-default |
| top | <node> |
color { } | always |
Creates a node like gsk_blend_node_new() with the given properties.
blur
| property | syntax | default | printed |
|---|---|---|---|
| blur | <number> |
1 | non-default |
| child | <node> |
color { } | always |
Creates a node like gsk_blur_node_new() with the given properties.
border
| property | syntax | default | printed |
|---|---|---|---|
| colors | <color>{1,4} |
black | non-default |
| outline | <rounded-rect> |
50 | always |
| widths | <number>{1,4} |
1 | non-default |
Creates a node like gsk_border_node_new() with the given properties.
For the color and width properties, the values follow the typical CSS order of top, right, bottom, left. If the last/left value isn't given, the 2nd/right value is used. If the 3rd/bottom value isn't given, the 1st/top value is used. And if the 2nd/right value also isn't given, the 1st/top value is used for every 4 values.
cairo
| property | syntax | default | printed |
|---|---|---|---|
| bounds | <rect> |
none | always |
| pixels | <url> |
none | non-default |
| script | <url> |
none | non-default |
The pixels are a base64-encoded data url of png data. The script is a base64-encoded data url of a cairo script.
clip
| property | syntax | default | printed |
|---|---|---|---|
| child | <node> |
color { } | always |
| clip | <rounded-rect> |
50 | always |
Creates a node like gsk_clip_node_new() with the given properties.
As an extension, this node allows specifying a rounded rectangle for the
clip property. If that rectangle is indeed rounded, a node like
gsk_rounded_clip_node_new() will be created instead.
color
| property | syntax | default | printed |
|---|---|---|---|
| bounds | <rect> |
50 | always |
| color | <color> |
#FF00CC | always |
Creates a node like gsk_color_node_new() with the given properties.
The color is chosen as an error pink so it is visible while also reminding people to change it.
color-matrix
| property | syntax | default | printed |
|---|---|---|---|
| child | <node> |
color { } | always |
| matrix | <transform> |
none | non-default |
| offset | <number>{4} |
0 0 0 0 | non-default |
Creates a node like gsk_color_matrix_node_new() with the given properties.
The matrix property accepts a for compatibility purposes, but you should be aware that the allowed values are meant to be used on 3D transformations, so their naming might appear awkward. However, it is always possible to use the matrix3d() production to specify all 16 values individually.
conic-gradient
| property | syntax | default | printed |
|---|---|---|---|
| bounds | <rect> |
50 | always |
| center | <point> |
25, 25 | always |
| rotation | <number> |
0 | always |
| stops | <color-stop> |
0 #AF0, 1 #F0C | always |
Creates a node like gsk_conic_gradient_node_new() with the given properties.
cross-fade
| property | syntax | default | printed |
|---|---|---|---|
| end | <node> |
color { } | always |
| progress | <number> |
0.5 | non-default |
| start | <node> |
color { } | always |
Creates a node like gsk_cross_fade_node_new() with the given properties.
debug
| property | syntax | default | printed |
|---|---|---|---|
| child | <node> |
color { } | always |
| message | <string> |
"" | non-default |
Creates a node like gsk_debug_node_new() with the given properties.
glshader
| property | syntax | default | printed |
|---|---|---|---|
| bounds | <rect> |
50 | always |
| sourcecode | <string> |
"" | always |
| args | <uniform values> |
none | non-default |
| child1 | <node> |
none | non-default |
| child2 | <node> |
none | non-default |
| child3 | <node> |
none | non-default |
| child4 | <node> |
none | non-default |
Creates a GLShader node. The sourcecode must be a GLSL fragment shader.
The args must match the uniforms of simple types declared in that shader,
in order and comma-separated. The child properties must match the sampler
uniforms in the shader.
inset-shadow
| property | syntax | default | printed |
|---|---|---|---|
| blur | <number> |
0 | non-default |
| color | <color> |
black | non-default |
| dx | <number> |
1 | non-default |
| dy | <number> |
1 | non-default |
| outline | <rounded-rect> |
50 | always |
| spread | <number> |
0 | non-default |
Creates a node like gsk_inset_shadow_node_new() with the given properties.
linear-gradient
| property | syntax | default | printed |
|---|---|---|---|
| bounds | <rect> |
50 | always |
| start | <point> |
0 0 | always |
| end | <point> |
0 50 | always |
| stops | <color-stop> |
0 #AF0, 1 #F0C | always |
Creates a node like gsk_linear_gradient_node_new() with the given properties.
mask
| property | syntax | default | printed |
|---|---|---|---|
| source | <node> |
color { } | always |
| mode | <mask-mode> |
alpha | non-default |
| mask | <node> |
color { } | always |
Creates a node like gsk_mask_node_new() with the given properties.
opacity
| property | syntax | default | printed |
|---|---|---|---|
| child | <node> |
color { } | always |
| opacity | <number> |
0.5 | non-default |
Creates a node like gsk_transform_node_new() with the given properties.
outset-shadow
| property | syntax | default | printed |
|---|---|---|---|
| blur | <number> |
0 | non-default |
| color | <color> |
black | non-default |
| dx | <number> |
1 | non-default |
| dy | <number> |
1 | non-default |
| outline | <rounded-rect> |
50 | always |
| spread | <number> |
0 | non-default |
Creates a node like gsk_outset_shadow_node_new() with the given properties.
radial-gradient
| property | syntax | default | printed |
|---|---|---|---|
| bounds | <rect> |
50 | always |
| center | <point> |
25 25 | always |
| hradius | <number> |
25 | always |
| vradius | <number> |
25 | always |
| start | <number> |
0 | always |
| end | <number> |
1 | always |
| stops | <color-stop> |
0 #AF0, 1 #F0C | always |
Creates a node like gsk_radial_gradient_node_new() with the given properties.
repeat
| property | syntax | default | printed |
|---|---|---|---|
| bounds | <rect> |
bounds of child node | non-default |
| child | <node> |
color { } | always |
| child-bounds | <rect> |
bounds of child node | non-default |
Creates a node like gsk_repeat_node_new() with the given properties.
repeating-linear-gradient
| property | syntax | default | printed |
|---|---|---|---|
| bounds | <rect> |
50 | always |
| start | <point> |
0 0 | always |
| end | <point> |
0 50 | always |
| stops | <color-stop> |
0 #AF0, 1 #F0C | always |
Creates a node like gsk_repeating_linear_gradient_node_new() with the given
properties.
repeating radial-gradient
| property | syntax | default | printed |
|---|---|---|---|
| bounds | <rect> |
50 | always |
| center | <point> |
25 25 | always |
| hradius | <number> |
25 | always |
| vradius | <number> |
25 | always |
| start | <number> |
0 | always |
| end | <number> |
1 | always |
| stops | <color-stop> |
0 #AF0, 1 #F0C | always |
Creates a node like gsk_repeating_radial_gradient_node_new() with the given
properties.
rounded-clip
| property | syntax | default | printed |
|---|---|---|---|
| child | <node> |
color { } | always |
| clip | <rounded-rect> |
50 | always |
Creates a node like gsk_rounded_clip_node_new() with the given properties.
shadow
| property | syntax | default | printed |
|---|---|---|---|
| child | <node> |
color { } | always |
| shadows | <shadow> |
black 1 1 | always |
Creates a node like gsk_shadow_node_new() with the given properties.
text
| property | syntax | default | printed |
|---|---|---|---|
| color | <color> |
black | non-default |
| font | <string> |
"Cantarell 11" | always |
| glyphs | <glyphs> |
"Hello" | always |
| offset | <point> |
0 0 | non-default |
Creates a node like gsk_text_node_new() with the given properties.
If the given font does not exist or the given glyphs are invalid for the given font, an error node will be returned.
texture
| property | syntax | default | printed |
|---|---|---|---|
| bounds | <rect> |
50 | always |
| texture | <url> |
see below | always |
Creates a node like gsk_texture_node_new() with the given properties.
The default texture is a 10x10 checkerboard with the top left and bottom right
5x5 being in the color #FF00CC and the other part being transparent. A possible
representation for this texture is url("data:image/png;base64,iVBORw0KGgoAAAANSUhEUgAAAAoAAAAKCAYAAACNMs+9AAAABmJLR0QA/wD/AP+gvaeTAAAAKUlEQVQYlWP8z3DmPwMaYGQwYUQXY0IXwAUGUCGGoxkYGBiweXAoeAYAz44F3e3U1xUAAAAASUVORK5CYII=") .
texture-scale
| property | syntax | default | printed |
|---|---|---|---|
| bounds | <rect> |
50 | always |
| texture | <url> |
see below | always |
| filter | filter |
see below | non-default |
Creates a node like gsk_texture_scale_node_new() with the given properties.
The default texture is a 10x10 checkerboard, just like for texture.
The possible filter values are linear, nearest and trilinear, with
linear being the default.
transform
| property | syntax | default | printed |
|---|---|---|---|
| child | <node> |
color { } | always |
| transform | <transform> |
none | non-default |
Creates a node like gsk_transform_node_new() with the given properties.