Selector

Selector is a implementation of JavaScripts querySelector. It is split between two files this file and the element package to prevent circular dependancys, however this document will be the source for it. The best way to explain how this works is to start in the element package with the querySelector method and then take a look at the parts that make it up.

flowchart LR;
    QuerySelector-->TestSelector;
    TestSelector-->GetCSSSelectors;
    GetCSSSelectors-->SplitSelector;
    SplitSelector-->Contains;
    Contains-->True;
    Contains-->False;
    False-->Children;
    True-->QuerySelector;
    EOL-->Yes;
    EOL-->No;
    No-->TestSelector
    Yes-->QuerySelector;
    Children-->TestSelector;
    Children-->EOL;

flowchart LR;
    QuerySelectorAll-->TestSelector;
    TestSelector-->GetCSSSelectors;
    GetCSSSelectors-->SplitSelector;
    SplitSelector-->Contains;
    Contains-->True;
    Contains-->False;
    False-->QuerySelectorAll;
    True-->EOL;
    EOL-->Yes;
    EOL-->No;
    No-->TestSelector
    Yes-->QuerySelectorAll;

# QuerySelector?(go)

QuerySelector works almost the same as JavaScripts querySelector method with a far limited scope. After a document is loaded from a HTML file it is compiled into element.Node's which is a custom implementation of net/html.Node. The reason the net/html node is not used is it has already defined features that stray away from JavaScripts DOM.

if TestSelector(selectString, n) {return n}

To start out, we check the current element to see if the selectString matches the element.Node (n) we called the method on using the TestSelector function. If it does we can end the function there and return itself. If it does not we can continue and check its children. We do this process recursively to simplify the code.

if cr.Properties.Id != "" {return cr}

We also do a check to see if the element.Node.Properties.Id has been assigned. This is a importaint step as this id is the the #id used in html but a unqiue id generated at run time to be used as a internal reference. If it has not been assigned then the element does not exist.

# QuerySelectorAll?(go)

See QuerySelector. QuerySelectorAll works the exact same as QuerySelector with an added collector (results) to collect all elements that match the selector throughout the recusive execution.

# TestSelector?(go)

TestSelector is the foundation of the QuerySelector and QuerySelectorAll as seen above.

parts := strings.Split(selectString, ">")

It first starts off by splitting the selectString in to parts divided by > this is becuase when you have a selector like blockquote > p you need to start at the first level (p) to compare the current node to see if you will need to continue to check the parents of the element with the next selector.

selectors := []string{} if n.Properties.Focusable { if n.Properties.Focused { selectors = append(selectors, ":focus") } } classes := n.ClassList.Classes for _, v := range classes { selectors = append(selectors, "."+v) }

Then we need to build the selectors, so we start by creating an array to store them in (s) and we check to see if the element is focusable and if the element is focused. If so we add the :focus selector to the list. This is important because when targeting a :focused element with a querySelector that is the text that is past. We then do the same for classes.

if n.Id != "" { selectors = append(selectors, "#"+n.Id) }

Then we add the id to the array to complete the current Nodes selectors.

part := selector.SplitSelector(strings.TrimSpace(parts[len(parts)-1])) has := selector.Contains(part, selectors)

After we have the current Nodes selectors we can use the SplitSelector and Contains methods to process the passed query (selectString) and compare the two arrays.

if len(parts) == 1 || !has { return has }

If we are on the last selector in the split selector (parts) or if we have a part that does not match (i.e. has == false) then we can go ahead and return the has value. We return this instead of just the constant false becuase if we have gotten to this point in the recursive chain that mean every part has been true until now, so the value of has weather true or false we detirmine if the selector matches for the entire selector string.

} else { return TestSelector(strings.Join(parts[0:len(parts)-1], ">"), n.Parent) }

If we are not on the last element and the selector matches for this Node then we can remove the last element from parts as we have already checked to make sure it matches and join it be > charectors as that is what it was split by at the beginning. Then we just recall the function passing the parent as the Node.

# SplitSelector?(go)

SplitSelector works by simply spliting a CSS selector into it's individual parts see below for an example:

1func main() {
2 fmt.Println(SplitSelector("p.text[name='first']"))
3}

Result

1[p .text [name='first']]

# Contains?(go)

Contains compares two arrays of selectors, the first argument is the array of the selector that will be use to detirmine if the Node is a match or not. The second argument is the selecter of the targeted Node, the Node need to have all of the selectors of the selector array, however it can have additional selectors and it will still match.

 1package selector
 2
 3import (
 4	"slices"
 5	"strings"
 6
 7	"golang.org/x/net/html"
 8)
 9
10// !ISSUE: Create :not and other selectors
11
12func GetInitCSSSelectors(node *html.Node, selectors []string) []string {
13	if node.Type == html.ElementNode {
14		selectors = append(selectors, node.Data)
15		for _, attr := range node.Attr {
16			if attr.Key == "class" {
17				classes := strings.Split(attr.Val, " ")
18				for _, class := range classes {
19					selectors = append(selectors, "."+class)
20				}
21			} else if attr.Key == "id" {
22				selectors = append(selectors, "#"+attr.Val)
23			} else {
24				selectors = append(selectors, "["+attr.Key+"=\""+attr.Val+"\"]")
25			}
26		}
27	}
28
29	return selectors
30}
31
32func SplitSelector(s string) []string {
33	var result []string
34	var current string
35
36	for _, char := range s {
37		switch char {
38		case '.', '#', '[', ']', ':':
39			if current != "" {
40				if string(char) == "]" {
41					current += string(char)
42				}
43				result = append(result, current)
44			}
45			current = ""
46			if string(char) != "]" {
47				current += string(char)
48			}
49		default:
50			current += string(char)
51		}
52	}
53
54	if current != "" && current != "]" {
55		result = append(result, current)
56	}
57
58	return result
59}
60
61func Contains(selector []string, node []string) bool {
62	has := true
63	for _, s := range selector {
64		if !slices.Contains(node, s) {
65			has = false
66		}
67	}
68	return has
69}

  1package element
  2
  3import (
  4	"fmt"
  5	"gui/selector"
  6	"image"
  7	ic "image/color"
  8	"math/rand"
  9	"strings"
 10
 11	"golang.org/x/image/font"
 12)
 13
 14type Node struct {
 15	TagName   string
 16	InnerText string
 17	InnerHTML string
 18	OuterHTML string
 19	Parent    *Node `json:"-"`
 20	Children  []Node
 21	Style     map[string]string
 22	Id        string
 23	ClassList ClassList
 24	Href      string
 25	Src       string
 26	Title     string
 27	Attribute map[string]string
 28
 29	ScrollY       float32
 30	Value         string
 31	OnClick       func(Event) `json:"-"`
 32	OnContextMenu func(Event) `json:"-"`
 33	OnMouseDown   func(Event) `json:"-"`
 34	OnMouseUp     func(Event) `json:"-"`
 35	OnMouseEnter  func(Event) `json:"-"`
 36	OnMouseLeave  func(Event) `json:"-"`
 37	OnMouseOver   func(Event) `json:"-"`
 38	OnMouseMove   func(Event) `json:"-"`
 39	OnScroll      func(Event) `json:"-"`
 40	Properties    Properties
 41}
 42
 43type State struct {
 44	// Id         string
 45	X          float32
 46	Y          float32
 47	Z          float32
 48	Width      float32
 49	Height     float32
 50	Border     Border
 51	Texture    *image.RGBA
 52	EM         float32
 53	Background ic.RGBA
 54	Color      ic.RGBA
 55	Hash       string
 56	Margin     MarginPadding
 57	Padding    MarginPadding
 58	Style      map[string]string
 59}
 60
 61// !FLAG: Plan to get rid of this
 62
 63type Properties struct {
 64	Id             string
 65	EventListeners map[string][]func(Event) `json:"-"`
 66	Focusable      bool
 67	Focused        bool
 68	Editable       bool
 69	Hover          bool
 70	Selected       []float32
 71}
 72
 73type ClassList struct {
 74	Classes []string
 75	Value   string
 76}
 77
 78type MarginPadding struct {
 79	Top    float32
 80	Left   float32
 81	Right  float32
 82	Bottom float32
 83}
 84
 85func (c *ClassList) Add(class string) {
 86	c.Classes = append(c.Classes, class)
 87	c.Value = strings.Join(c.Classes, " ")
 88}
 89
 90func (c *ClassList) Remove(class string) {
 91	for i, v := range c.Classes {
 92		if v == class {
 93			c.Classes = append(c.Classes[:i], c.Classes[i+1:]...)
 94			break
 95		}
 96	}
 97
 98	c.Value = strings.Join(c.Classes, " ")
 99}
100
101type Border struct {
102	Width  float32
103	Style  string
104	Color  ic.RGBA
105	Radius string
106}
107
108type Text struct {
109	Font                font.Face
110	Color               ic.RGBA
111	Text                string
112	Underlined          bool
113	Overlined           bool
114	LineThrough         bool
115	DecorationColor     ic.RGBA
116	DecorationThickness int
117	Align               string
118	Indent              int // very low priority
119	LetterSpacing       int
120	LineHeight          int
121	WordSpacing         int
122	WhiteSpace          string
123	Shadows             []Shadow // need
124	Width               int
125	WordBreak           string
126	EM                  int
127	X                   int
128	LoadedFont          string
129}
130
131type Shadow struct {
132	X     int
133	Y     int
134	Blur  int
135	Color ic.RGBA
136}
137
138func (n *Node) GetAttribute(name string) string {
139	return n.Attribute[name]
140}
141
142func (n *Node) SetAttribute(key, value string) {
143	n.Attribute[key] = value
144}
145
146func (n *Node) CreateElement(name string) Node {
147	return Node{
148		TagName:   name,
149		InnerText: "",
150		OuterHTML: "",
151		InnerHTML: "",
152		Children:  []Node{},
153		Style:     make(map[string]string),
154		Id:        "",
155		ClassList: ClassList{
156			Classes: []string{},
157			Value:   "",
158		},
159		Href:      "",
160		Src:       "",
161		Title:     "",
162		Attribute: make(map[string]string),
163		Value:     "",
164		Properties: Properties{
165			Id:             "",
166			EventListeners: make(map[string][]func(Event)),
167			Focusable:      false,
168			Focused:        false,
169			Editable:       false,
170			Hover:          false,
171			Selected:       []float32{},
172		},
173	}
174}
175
176func (n *Node) QuerySelectorAll(selectString string) *[]*Node {
177	results := []*Node{}
178	if TestSelector(selectString, n) {
179		results = append(results, n)
180	}
181
182	for i := range n.Children {
183		el := &n.Children[i]
184		cr := el.QuerySelectorAll(selectString)
185		if len(*cr) > 0 {
186			results = append(results, *cr...)
187		}
188	}
189	return &results
190}
191
192func (n *Node) QuerySelector(selectString string) *Node {
193	if TestSelector(selectString, n) {
194		return n
195	}
196
197	for i := range n.Children {
198		el := &n.Children[i]
199		cr := el.QuerySelector(selectString)
200		if cr.Properties.Id != "" {
201			return cr
202		}
203	}
204
205	return &Node{}
206}
207
208func TestSelector(selectString string, n *Node) bool {
209	parts := strings.Split(selectString, ">")
210
211	selectors := []string{}
212	if n.Properties.Focusable {
213		if n.Properties.Focused {
214			selectors = append(selectors, ":focus")
215		}
216	}
217
218	classes := n.ClassList.Classes
219
220	for _, v := range classes {
221		selectors = append(selectors, "."+v)
222	}
223
224	if n.Id != "" {
225		selectors = append(selectors, "#"+n.Id)
226	}
227
228	selectors = append(selectors, n.TagName)
229
230	part := selector.SplitSelector(strings.TrimSpace(parts[len(parts)-1]))
231
232	has := selector.Contains(part, selectors)
233
234	if len(parts) == 1 || !has {
235		return has
236	} else {
237		return TestSelector(strings.Join(parts[0:len(parts)-1], ">"), n.Parent)
238	}
239}
240
241func (n *Node) AppendChild(c Node) {
242	c.Parent = n
243	// Set Id
244	randomInt := rand.Intn(10000)
245
246	c.Properties.Id = c.TagName + fmt.Sprint(randomInt+len(c.Parent.Children))
247
248	n.Children = append(n.Children, c)
249}
250
251func (n *Node) InsertAfter(c, tgt Node) {
252	c.Parent = n
253	// Set Id
254	randomInt := rand.Intn(10000)
255
256	c.Properties.Id = c.TagName + fmt.Sprint(randomInt+len(c.Parent.Children))
257	nodeIndex := -1
258	for i, v := range n.Children {
259
260		if v.Properties.Id == tgt.Properties.Id {
261			nodeIndex = i
262			break
263		}
264	}
265	if nodeIndex > -1 {
266		n.Children = append(n.Children[:nodeIndex+1], append([]Node{c}, n.Children[nodeIndex+1:]...)...)
267	} else {
268		n.AppendChild(c)
269	}
270}
271
272func (n *Node) InsertBefore(c, tgt Node) {
273	c.Parent = n
274	// Set Id
275	randomInt := rand.Intn(10000)
276
277	c.Properties.Id = c.TagName + fmt.Sprint(randomInt+len(c.Parent.Children))
278	nodeIndex := -1
279	for i, v := range n.Children {
280		if v.Properties.Id == tgt.Properties.Id {
281			nodeIndex = i
282			break
283		}
284	}
285	if nodeIndex > 0 {
286		n.Children = append(n.Children[:nodeIndex], append([]Node{c}, n.Children[nodeIndex:]...)...)
287	} else {
288		n.AppendChild(c)
289	}
290
291}
292
293func (n *Node) Remove() {
294	nodeIndex := -1
295	for i, v := range n.Parent.Children {
296		if v.Properties.Id == n.Properties.Id {
297			nodeIndex = i
298			break
299		}
300	}
301	if nodeIndex > 0 {
302		n.Parent.Children = append(n.Parent.Children[:nodeIndex], n.Parent.Children[nodeIndex+1:]...)
303	}
304}
305
306func (n *Node) Focus() {
307	if n.Properties.Focusable {
308		n.Properties.Focused = true
309		n.ClassList.Add(":focus")
310	}
311}
312
313func (n *Node) Blur() {
314	if n.Properties.Focusable {
315		n.Properties.Focused = false
316		n.ClassList.Remove(":focus")
317	}
318}
319
320type Event struct {
321	X           int
322	Y           int
323	KeyCode     int
324	Key         string
325	CtrlKey     bool
326	MetaKey     bool
327	ShiftKey    bool
328	AltKey      bool
329	Click       bool
330	ContextMenu bool
331	MouseDown   bool
332	MouseUp     bool
333	MouseEnter  bool
334	MouseLeave  bool
335	MouseOver   bool
336	KeyUp       bool
337	KeyDown     bool
338	KeyPress    bool
339	Input       bool
340	Target      Node
341}
342
343type EventList struct {
344	Event Event
345	List  []string
346}
347
348func (node *Node) AddEventListener(name string, callback func(Event)) {
349	if node.Properties.EventListeners == nil {
350		node.Properties.EventListeners = make(map[string][]func(Event))
351	}
352	if node.Properties.EventListeners[name] == nil {
353		node.Properties.EventListeners[name] = []func(Event){}
354	}
355	node.Properties.EventListeners[name] = append(node.Properties.EventListeners[name], callback)
356}