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.

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

selectors := selector.GetCSSSelectors(n.Properties.Node, s)

Next we use the GetCSSSelectors method in this package to generate any selectors assigned to the net/html Node.

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.

# GetCSSSelectors?(go)

GetCSSSelectors purpose is to generate all possible selectors for a net/html Node. It is used inside of the element package interally to the TestSelector function. It does this buy taking the classes, id's, and attributes and creating an array of their string equalivents (.class, #id, and [value="somevalue"]).

# 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
 10func GetCSSSelectors(node *html.Node, selectors []string) []string {
 11	if node.Type == html.ElementNode {
 12		selectors = append(selectors, node.Data)
 13		for _, attr := range node.Attr {
 14			if attr.Key == "class" {
 15				classes := strings.Split(attr.Val, " ")
 16				for _, class := range classes {
 17					selectors = append(selectors, "."+class)
 18				}
 19			} else if attr.Key == "id" {
 20				selectors = append(selectors, "#"+attr.Val)
 21			} else {
 22				selectors = append(selectors, "["+attr.Key+"=\""+attr.Val+"\"]")
 23			}
 24		}
 25	}
 26
 27	return selectors
 28}
 29
 30func SplitSelector(s string) []string {
 31	var result []string
 32	var current string
 33
 34	for _, char := range s {
 35		switch char {
 36		case '.', '#', '[', ']', ':':
 37			if current != "" {
 38				if string(char) == "]" {
 39					current += string(char)
 40				}
 41				result = append(result, current)
 42			}
 43			current = ""
 44			if string(char) != "]" {
 45				current += string(char)
 46			}
 47		default:
 48			current += string(char)
 49		}
 50	}
 51
 52	if current != "" && current != "]" {
 53		result = append(result, current)
 54	}
 55
 56	return result
 57}
 58
 59func Contains(selector []string, node []string) bool {
 60	has := true
 61	for _, s := range selector {
 62		if !slices.Contains(node, s) {
 63			has = false
 64		}
 65	}
 66	return has
 67}
 68
 69// func Query(selector string, n *Node) bool {
 70// 	parts := strings.Split(selector, ">")
 71
 72// 	selectors := getCSSSelectors(n.Node, []string{})
 73
 74// 	part := splitSelector(strings.TrimSpace(parts[len(parts)-1]))
 75
 76// 	fmt.Println(part, selectors)
 77
 78// 	has := contains(part, selectors)
 79
 80// 	if len(parts) == 1 || !has {
 81// 		return has
 82// 	} else {
 83// 		return Query(strings.Join(parts[0:len(parts)-1], ">"), n.Parent)
 84// 	}
 85// }
 86
 87// func main() {
 88// 	selector := "div.class#id[attr=\"value\"] > div"
 89
 90// 	node := &html.Node{
 91// 		Type: html.ElementNode,
 92// 		Data: "div",
 93// 		Attr: []html.Attribute{
 94// 			{Key: "class", Val: "class"},
 95// 			{Key: "id", Val: "id"},
 96// 			{Key: "attr", Val: "value"},
 97// 		},
 98// 	}
 99
100// 	nodeparent := &html.Node{
101// 		Type: html.ElementNode,
102// 		Data: "div",
103// 		Attr: []html.Attribute{
104// 			{Key: "class", Val: "class"},
105// 			{Key: "id", Val: "id"},
106// 			{Key: "attr", Val: "value"},
107// 		},
108// 	}
109
110// 	n := Node{
111// 		Node: node,
112// 		Parent: &Node{
113// 			Node: nodeparent,
114// 		},
115// 	}
116
117// 	fmt.Println(Query(selector, &n))
118// }

  1package element
  2
  3import (
  4	"gui/selector"
  5	"image"
  6	ic "image/color"
  7	"strings"
  8
  9	"golang.org/x/image/font"
 10
 11	"golang.org/x/net/html"
 12)
 13
 14type Node struct {
 15	TagName   string
 16	InnerText string
 17	Parent    *Node
 18	Children  []Node
 19	Style     map[string]string
 20	Id        string
 21	ClassList ClassList
 22	Href      string
 23	Src       string
 24	Title     string
 25
 26	ScrollY       float32
 27	Value         string
 28	OnClick       func(Event)
 29	OnContextMenu func(Event)
 30	OnMouseDown   func(Event)
 31	OnMouseUp     func(Event)
 32	OnMouseEnter  func(Event)
 33	OnMouseLeave  func(Event)
 34	OnMouseOver   func(Event)
 35	OnMouseMove   func(Event)
 36	OnScroll      func(Event)
 37	Properties    Properties
 38}
 39
 40type Properties struct {
 41	Node           *html.Node
 42	Type           html.NodeType
 43	Id             string
 44	X              float32
 45	Y              float32
 46	Hash           string
 47	Width          float32
 48	Height         float32
 49	Border         Border
 50	EventListeners map[string][]func(Event)
 51	EM             float32
 52	Text           Text
 53	Focusable      bool
 54	Focused        bool
 55	Editable       bool
 56	Hover          bool
 57	Selected       []float32
 58	Test           string
 59}
 60
 61type ClassList struct {
 62	Classes []string
 63	Value   string
 64}
 65
 66func (c *ClassList) Add(class string) {
 67	c.Classes = append(c.Classes, class)
 68	c.Value = strings.Join(c.Classes, " ")
 69}
 70
 71func (c *ClassList) Remove(class string) {
 72	for i, v := range c.Classes {
 73		if v == class {
 74			c.Classes = append(c.Classes[:i], c.Classes[i+1:]...)
 75			break
 76		}
 77	}
 78
 79	c.Value = strings.Join(c.Classes, " ")
 80}
 81
 82type Border struct {
 83	Width  string
 84	Style  string
 85	Color  ic.RGBA
 86	Radius string
 87}
 88
 89type Text struct {
 90	Font                font.Face
 91	Color               ic.RGBA
 92	Image               *image.RGBA
 93	Underlined          bool
 94	Overlined           bool
 95	LineThrough         bool
 96	DecorationColor     ic.RGBA
 97	DecorationThickness int
 98	Align               string
 99	Indent              int // very low priority
100	LetterSpacing       int
101	LineHeight          int
102	WordSpacing         int
103	WhiteSpace          string
104	Shadows             []Shadow // need
105	Width               int
106	WordBreak           string
107	EM                  int
108	X                   int
109	LoadedFont          string
110}
111
112type Shadow struct {
113	X     int
114	Y     int
115	Blur  int
116	Color ic.RGBA
117}
118
119func (n *Node) GetAttribute(name string) string {
120	attributes := make(map[string]string)
121
122	for _, attr := range n.Properties.Node.Attr {
123		attributes[attr.Key] = attr.Val
124	}
125	return attributes[name]
126}
127
128func (n *Node) SetAttribute(key, value string) {
129	// Iterate through the attributes
130	for i, attr := range n.Properties.Node.Attr {
131		// If the attribute key matches, update its value
132		if attr.Key == key {
133			n.Properties.Node.Attr[i].Val = value
134			return
135		}
136	}
137
138	// If the attribute key was not found, add a new attribute
139	n.Properties.Node.Attr = append(n.Properties.Node.Attr, html.Attribute{
140		Key: key,
141		Val: value,
142	})
143}
144
145func (n *Node) QuerySelectorAll(selectString string) *[]*Node {
146	results := []*Node{}
147	if TestSelector(selectString, n) {
148		results = append(results, n)
149	}
150
151	for i := range n.Children {
152		el := &n.Children[i]
153		cr := el.QuerySelectorAll(selectString)
154		if len(*cr) > 0 {
155			results = append(results, *cr...)
156		}
157	}
158	return &results
159}
160
161func (n *Node) QuerySelector(selectString string) *Node {
162	if TestSelector(selectString, n) {
163		return n
164	}
165
166	for i := range n.Children {
167		el := &n.Children[i]
168		cr := el.QuerySelector(selectString)
169		if cr.Properties.Id != "" {
170			return cr
171		}
172	}
173
174	return &Node{}
175}
176
177func TestSelector(selectString string, n *Node) bool {
178	parts := strings.Split(selectString, ">")
179
180	s := []string{}
181	if n.Properties.Focusable {
182		if n.Properties.Focused {
183			s = append(s, ":focus")
184		}
185	}
186
187	classes := n.ClassList.Classes
188
189	for _, v := range classes {
190		s = append(s, "."+v)
191	}
192	// fmt.Println(n.Properties.Node)
193	selectors := selector.GetCSSSelectors(n.Properties.Node, s)
194	if n.Id != "" {
195		selectors = append(selectors, "#"+n.Id)
196	}
197
198	part := selector.SplitSelector(strings.TrimSpace(parts[len(parts)-1]))
199
200	has := selector.Contains(part, selectors)
201
202	if len(parts) == 1 || !has {
203		return has
204	} else {
205		return TestSelector(strings.Join(parts[0:len(parts)-1], ">"), n.Parent)
206	}
207}
208
209func (n *Node) AppendChild(c Node) {
210	c.Parent = n
211	n.Children = append(n.Children, c)
212}
213
214func (n *Node) Focus() {
215	if n.Properties.Focusable {
216		n.Properties.Focused = true
217		n.ClassList.Add(":focus")
218	}
219}
220
221func (n *Node) Blur() {
222	if n.Properties.Focusable {
223		n.Properties.Focused = false
224		n.ClassList.Remove(":focus")
225	}
226}
227
228type Event struct {
229	X           int
230	Y           int
231	KeyCode     int
232	Key         string
233	CtrlKey     bool
234	MetaKey     bool
235	ShiftKey    bool
236	AltKey      bool
237	Click       bool
238	ContextMenu bool
239	MouseDown   bool
240	MouseUp     bool
241	MouseEnter  bool
242	MouseLeave  bool
243	MouseOver   bool
244	KeyUp       bool
245	KeyDown     bool
246	KeyPress    bool
247	Input       bool
248	Target      Node
249}
250
251type EventList struct {
252	Event Event
253	List  []string
254}
255
256func (node *Node) AddEventListener(name string, callback func(Event)) {
257	if node.Properties.EventListeners == nil {
258		node.Properties.EventListeners = make(map[string][]func(Event))
259	}
260	if node.Properties.EventListeners[name] == nil {
261		node.Properties.EventListeners[name] = []func(Event){}
262	}
263	node.Properties.EventListeners[name] = append(node.Properties.EventListeners[name], callback)
264}