CStyle Plugins

Plugins add the ability to choose what parts of the HTML/CSS spec you add to your application. If you are trying to keep compile sizes small you can remove as many as you need to reach your target size. Here we will go over the basics of how they work and how to use them.

The difference between plugins and transformers is, plugins have a order when they need to be executed and run after the state has been initialised. Transformers on the other hand require nothing but the DOM and the init style definitions. Transformers are used to transform things like an ul tag into a simpler div structure and plugins are used mainly to compute styles outside of the main function (see flex, inline, etc...).

1type Plugin struct {
2	Selector func(*element.Node) bool
3	Level   int
4	Handler func(*element.Node, *map[string]element.State)
5}

A plugin is a struct defined in CStyle, in contains three properties:

• Selector
  • A function that determines if the plugin should run.
• Level
  • Level of priority in which to execute
  • All library level should be between 0 and 2
    • All others should be greater than 2
• Handler
  • Callback function that provides a pointer to a element that matches the properties of Styles

# AddPlugin?(go)

Add Plugin is the CStyle function that add the plugin to the top level cstyle.Plugins array where it is used within the ComputeNodeStyle function.

# Usage

1css.AddPlugin(block.Init())

The first step in processing the plugins before running there handler functions is to sort them by their levels. We need to sort the plugins by their level because in the example of flex, it relys on a parent element being block position so it can compute styles based of the positioning of its parent elements. If flex was ran before block then it would have nothing to build apon. This is also the reason that if you are building a custom plugin it is reccomended to keep the level above 2 as anything after 2 will have the assumed styles to build apon.

// Sorting the array by the Level field sort.Slice(plugins, func(i, j int) bool { return plugins[i].Level < plugins[j].Level })

After we have the sorted plugins we can check if the current element matches the Styles of the plugin. The matching is a all of nothing matching system, if one property is missing then the plugin wil not be ran. If it does match then a pointer to the element.Node (n) is passed to the handler.

for _, v := range plugins { matches := true for name, value := range v.Styles { if styleMap[name] != value && !(value == "*") { matches = false } } if matches { v.Handler(n) } }

# plugins/block

Here is the code for the block styling plugin, it is recommended to keep this standard format.

All other plugins can be found in the cstyle/plugins folder

 1package block
 2
 3import (
 4	"gui/cstyle"
 5	"gui/element"
 6)
 7
 8func Init() cstyle.Plugin {
 9	return cstyle.Plugin{
10		Selector: func(n *element.Node) bool {
11			styles := map[string]string{
12				"display": "block",
13			}
14			matches := true
15			for name, value := range styles {
16				if n.Style[name] != value && !(value == "*") && n.Style[name] != "" {
17					matches = false
18				}
19			}
20			return matches
21		},
22		Level: 0,
23		Handler: func(n *element.Node, state *map[string]element.State) {
24			s := *state
25			self := s[n.Properties.Id]
26			// parent := s[n.Parent.Properties.Id]
27
28			// If the element is display block and the width is unset then make it 100%
29
30			// if self.Style["width"] == "" {
31			// 	self.Width, _ = utils.ConvertToPixels("100%", self.EM, parent.Width)
32			// 	fmt.Println(self.Margin)
33
34			// 	// self.Width -= (self.Padding.Right + self.Padding.Left)
35			// 	// self.Height -= (self.Padding.Top + self.Padding.Bottom)
36			// }
37
38			// if self.X+self.Width+(self.Border.Width*2) > parent.Width {
39			// 	self.Width = parent.Width
40			// 	self.Width -= (self.Margin.Right + self.Margin.Left)
41			// 	self.Width -= (self.Border.Width * 2)
42			// 	self.Height -= (self.Margin.Top + self.Margin.Bottom)
43			// }
44
45			(*state)[n.Properties.Id] = self
46		},
47	}
48}

  1package cstyle
  2
  3import (
  4	"fmt"
  5	"gui/color"
  6	"gui/element"
  7	"gui/font"
  8	"gui/parser"
  9	"gui/utils"
 10	"os"
 11	"slices"
 12	"sort"
 13	"strconv"
 14	"strings"
 15)
 16
 17// !TODO: Make a fine selector to target tags and if it has children or not etc
 18// + could copy the transformers but idk
 19type Plugin struct {
 20	Selector func(*element.Node) bool
 21	Level    int
 22	Handler  func(*element.Node, *map[string]element.State)
 23}
 24
 25type Transformer struct {
 26	Selector func(*element.Node) bool
 27	Handler  func(element.Node, *CSS) element.Node
 28}
 29
 30type CSS struct {
 31	Width        float32
 32	Height       float32
 33	StyleSheets  []map[string]map[string]string
 34	Plugins      []Plugin
 35	Transformers []Transformer
 36	Document     *element.Node
 37}
 38
 39func (c *CSS) Transform(n element.Node) element.Node {
 40	for _, v := range c.Transformers {
 41		if v.Selector(&n) {
 42			n = v.Handler(n, c)
 43		}
 44	}
 45	for i := 0; i < len(n.Children); i++ {
 46		v := n.Children[i]
 47		tc := c.Transform(v)
 48		n = *tc.Parent
 49		n.Children[i] = tc
 50	}
 51
 52	return n
 53}
 54
 55func (c *CSS) StyleSheet(path string) {
 56	// Parse the CSS file
 57	dat, _ := os.ReadFile(path)
 58	styles := parser.ParseCSS(string(dat))
 59
 60	c.StyleSheets = append(c.StyleSheets, styles)
 61}
 62
 63func (c *CSS) StyleTag(css string) {
 64	styles := parser.ParseCSS(css)
 65	c.StyleSheets = append(c.StyleSheets, styles)
 66}
 67
 68var inheritedProps = []string{
 69	"color",
 70	"cursor",
 71	"font",
 72	"font-family",
 73	"font-size",
 74	"font-style",
 75	"font-weight",
 76	"letter-spacing",
 77	"line-height",
 78	// "text-align",
 79	"text-indent",
 80	"text-justify",
 81	"text-shadow",
 82	"text-transform",
 83	"text-decoration",
 84	"visibility",
 85	"word-spacing",
 86	"display",
 87}
 88
 89func (c *CSS) GetStyles(n element.Node) map[string]string {
 90	styles := map[string]string{}
 91
 92	if n.Parent != nil {
 93		ps := c.GetStyles(*n.Parent)
 94		for _, v := range inheritedProps {
 95			if ps[v] != "" {
 96				styles[v] = ps[v]
 97			}
 98		}
 99	}
100	for k, v := range n.Style {
101		styles[k] = v
102	}
103	hovered := false
104	if slices.Contains(n.ClassList.Classes, ":hover") {
105		hovered = true
106	}
107
108	for _, styleSheet := range c.StyleSheets {
109		for selector := range styleSheet {
110			// fmt.Println(selector, n.Properties.Id)
111			key := selector
112			if strings.Contains(selector, ":hover") && hovered {
113				selector = strings.Replace(selector, ":hover", "", -1)
114			}
115			if element.TestSelector(selector, &n) {
116				for k, v := range styleSheet[key] {
117					styles[k] = v
118				}
119			}
120
121		}
122	}
123
124	// This is different than node.Style
125	// temp1 = <span style=​"color:​#a6e22e">​CSS​</span>​
126	// temp1.style == CSSStyleDeclaration {0: 'color', accentColor: '', additiveSymbols: '', alignContent: '', alignItems: '', alignSelf: '', …}
127	// temp1.getAttribute("style") == 'color:#a6e22e'
128	inline := parser.ParseStyleAttribute(n.GetAttribute("style") + ";")
129	styles = utils.Merge(styles, inline)
130	// add hover and focus css events
131
132	if n.Parent != nil {
133		if styles["z-index"] == "" && n.Parent.Style["z-index"] != "" {
134			z, _ := strconv.Atoi(n.Parent.Style["z-index"])
135			z += 1
136			styles["z-index"] = strconv.Itoa(z)
137		}
138	}
139
140	return styles
141}
142
143func (c *CSS) AddPlugin(plugin Plugin) {
144	c.Plugins = append(c.Plugins, plugin)
145}
146
147func (c *CSS) AddTransformer(transformer Transformer) {
148	c.Transformers = append(c.Transformers, transformer)
149}
150
151func CheckNode(n *element.Node, state *map[string]element.State) {
152	s := *state
153	self := s[n.Properties.Id]
154
155	fmt.Println(n.TagName, n.Properties.Id)
156	fmt.Printf("ID: %v\n", n.Id)
157	fmt.Printf("EM: %v\n", self.EM)
158	fmt.Printf("Parent: %v\n", n.Parent.TagName)
159	fmt.Printf("Classes: %v\n", n.ClassList.Classes)
160	fmt.Printf("Text: %v\n", n.InnerText)
161	fmt.Printf("X: %v, Y: %v, Z: %v\n", self.X, self.Y, self.Z)
162	fmt.Printf("Width: %v, Height: %v\n", self.Width, self.Height)
163	fmt.Printf("Styles: %v\n", n.Style)
164	// fmt.Printf("Background: %v\n", self.Background)
165	// fmt.Printf("Border: %v\n\n\n", self.Border)
166}
167
168func (c *CSS) ComputeNodeStyle(n *element.Node, state *map[string]element.State) *element.Node {
169
170	// Head is not renderable
171	if utils.IsParent(*n, "head") {
172		return n
173	}
174
175	plugins := c.Plugins
176
177	s := *state
178	self := s[n.Properties.Id]
179	parent := s[n.Parent.Properties.Id]
180
181	self.Background = color.Parse(n.Style, "background")
182	self.Border, _ = CompleteBorder(n.Style, self, parent)
183
184	fs, _ := utils.ConvertToPixels(n.Style["font-size"], parent.EM, parent.Width)
185	self.EM = fs
186
187	if n.Style["display"] == "none" {
188		self.X = 0
189		self.Y = 0
190		self.Width = 0
191		self.Height = 0
192		return n
193	}
194
195	// Set Z index value to be sorted in window
196	if n.Style["z-index"] != "" {
197		z, _ := strconv.Atoi(n.Style["z-index"])
198		self.Z = float32(z)
199	}
200
201	if parent.Z > 0 {
202		self.Z = parent.Z + 1
203	}
204
205	(*state)[n.Properties.Id] = self
206
207	wh := utils.GetWH(*n, state)
208	width := wh.Width
209	height := wh.Height
210
211	x, y := parent.X, parent.Y
212	// !NOTE: Would like to consolidate all XY function into this function like WH
213	offsetX, offsetY := utils.GetXY(n, state)
214	x += offsetX
215	y += offsetY
216
217	var top, left, right, bottom bool = false, false, false, false
218
219	m := utils.GetMP(*n, wh, state, "margin")
220	p := utils.GetMP(*n, wh, state, "padding")
221
222	self.Margin = m
223	self.Padding = p
224
225	if n.Style["position"] == "absolute" {
226		bas := utils.GetPositionOffsetNode(n)
227		base := s[bas.Properties.Id]
228		if n.Style["top"] != "" {
229			v, _ := utils.ConvertToPixels(n.Style["top"], self.EM, parent.Width)
230			y = v + base.Y
231			top = true
232		}
233		if n.Style["left"] != "" {
234			v, _ := utils.ConvertToPixels(n.Style["left"], self.EM, parent.Width)
235			x = v + base.X
236			left = true
237		}
238		if n.Style["right"] != "" {
239			v, _ := utils.ConvertToPixels(n.Style["right"], self.EM, parent.Width)
240			x = (base.Width - width) - v
241			right = true
242		}
243		if n.Style["bottom"] != "" {
244			v, _ := utils.ConvertToPixels(n.Style["bottom"], self.EM, parent.Width)
245			y = (base.Height - height) - v
246			bottom = true
247		}
248
249	} else {
250		for i, v := range n.Parent.Children {
251			if v.Style["position"] != "absolute" {
252				if v.Properties.Id == n.Properties.Id {
253					if i-1 > 0 {
254						sib := n.Parent.Children[i-1]
255						sibling := s[sib.Properties.Id]
256						if sib.Style["position"] != "absolute" {
257							if n.Style["display"] == "inline" {
258								if sib.Style["display"] == "inline" {
259									y = sibling.Y
260								} else {
261									y = sibling.Y + sibling.Height
262								}
263							} else {
264								y = sibling.Y + sibling.Height + (sibling.Border.Width * 2) + sibling.Margin.Bottom
265							}
266						}
267
268					}
269					break
270				} else if n.Style["display"] != "inline" {
271					vState := s[v.Properties.Id]
272					y += vState.Margin.Top + vState.Margin.Bottom + vState.Padding.Top + vState.Padding.Bottom + vState.Height + (self.Border.Width)
273				}
274			}
275		}
276	}
277
278	// Display modes need to be calculated here
279
280	relPos := !top && !left && !right && !bottom
281
282	if left || relPos {
283		x += m.Left
284	}
285	if top || relPos {
286		y += m.Top
287	}
288	if right {
289		x -= m.Right
290	}
291	if bottom {
292		y -= m.Bottom
293	}
294
295	self.X = x
296	self.Y = y
297	self.Width = width
298	self.Height = height
299	(*state)[n.Properties.Id] = self
300
301	if !utils.ChildrenHaveText(n) && len(n.InnerText) > 0 {
302		// Confirm text exists
303		if len(strings.TrimSpace(n.InnerText)) > 0 {
304			n.InnerText = strings.TrimSpace(n.InnerText)
305			self = genTextNode(n, state)
306		}
307	}
308
309	(*state)[n.Properties.Id] = self
310	(*state)[n.Parent.Properties.Id] = parent
311
312	// Call children here
313	// !TODO: Make something that stops rendering things out of fov
314	fmt.Println("!HER", n.Properties.Id, self.Width, self.Height)
315
316	if self.Y < c.Height {
317		var childYOffset float32
318		for i := 0; i < len(n.Children); i++ {
319			v := n.Children[i]
320			v.Parent = n
321			// This is were the tainting comes from
322			n.Children[i] = *c.ComputeNodeStyle(&v, state)
323
324			cState := (*state)[n.Children[i].Properties.Id]
325			if n.Style["height"] == "" {
326				if v.Style["position"] != "absolute" && cState.Y+cState.Height > childYOffset {
327					childYOffset = cState.Y + cState.Height
328					self.Height = (cState.Y - self.Border.Width) - (self.Y) + cState.Height
329					self.Height += cState.Margin.Top
330					self.Height += cState.Margin.Bottom
331					self.Height += cState.Padding.Top
332					self.Height += cState.Padding.Bottom
333				}
334			}
335			if cState.Width > self.Width {
336				self.Width = cState.Width
337			}
338		}
339	} else {
340		return n
341	}
342
343	self.Height += self.Padding.Bottom
344
345	(*state)[n.Properties.Id] = self
346
347	// Sorting the array by the Level field
348	sort.Slice(plugins, func(i, j int) bool {
349		return plugins[i].Level < plugins[j].Level
350	})
351
352	for _, v := range plugins {
353		if v.Selector(n) {
354			v.Handler(n, state)
355		}
356	}
357
358	CheckNode(n, state)
359
360	return n
361}
362
363func CompleteBorder(cssProperties map[string]string, self, parent element.State) (element.Border, error) {
364	// Split the shorthand into components
365	borderComponents := strings.Fields(cssProperties["border"])
366
367	// Ensure there are at least 1 component (width or style or color)
368	if len(borderComponents) >= 1 {
369		width := "0px" // Default width
370		style := "solid"
371		borderColor := "#000000" // Default color
372
373		// Extract style and color if available
374		if len(borderComponents) >= 1 {
375			width = borderComponents[0]
376		}
377
378		// Extract style and color if available
379		if len(borderComponents) >= 2 {
380			style = borderComponents[1]
381		}
382		if len(borderComponents) >= 3 {
383			borderColor = borderComponents[2]
384		}
385
386		parsedColor, _ := color.Color(borderColor)
387
388		w, _ := utils.ConvertToPixels(width, self.EM, parent.Width)
389
390		return element.Border{
391			Width:  w,
392			Style:  style,
393			Color:  parsedColor,
394			Radius: cssProperties["border-radius"],
395		}, nil
396	}
397
398	return element.Border{}, fmt.Errorf("invalid border shorthand format")
399}
400
401func genTextNode(n *element.Node, state *map[string]element.State) element.State {
402	s := *state
403	self := s[n.Properties.Id]
404	parent := s[n.Parent.Properties.Id]
405
406	text := element.Text{}
407
408	bold, italic := false, false
409
410	if n.Style["font-weight"] == "bold" {
411		bold = true
412	}
413
414	if n.Style["font-style"] == "italic" {
415		italic = true
416	}
417
418	if text.Font == nil {
419		f, _ := font.LoadFont(n.Style["font-family"], int(self.EM), bold, italic)
420		text.Font = f
421	}
422
423	letterSpacing, _ := utils.ConvertToPixels(n.Style["letter-spacing"], self.EM, parent.Width)
424	wordSpacing, _ := utils.ConvertToPixels(n.Style["word-spacing"], self.EM, parent.Width)
425	lineHeight, _ := utils.ConvertToPixels(n.Style["line-height"], self.EM, parent.Width)
426	if lineHeight == 0 {
427		lineHeight = self.EM + 3
428	}
429
430	text.LineHeight = int(lineHeight)
431	text.WordSpacing = int(wordSpacing)
432	text.LetterSpacing = int(letterSpacing)
433	wb := " "
434
435	if n.Style["word-wrap"] == "break-word" {
436		wb = ""
437	}
438
439	if n.Style["text-wrap"] == "wrap" || n.Style["text-wrap"] == "balance" {
440		wb = ""
441	}
442
443	var dt float32
444
445	if n.Style["text-decoration-thickness"] == "auto" || n.Style["text-decoration-thickness"] == "" {
446		dt = self.EM / 7
447	} else {
448		dt, _ = utils.ConvertToPixels(n.Style["text-decoration-thickness"], self.EM, parent.Width)
449	}
450
451	col := color.Parse(n.Style, "font")
452
453	self.Color = col
454
455	text.Color = col
456	text.DecorationColor = color.Parse(n.Style, "decoration")
457	text.Align = n.Style["text-align"]
458	text.WordBreak = wb
459	text.WordSpacing = int(wordSpacing)
460	text.LetterSpacing = int(letterSpacing)
461	text.WhiteSpace = n.Style["white-space"]
462	text.DecorationThickness = int(dt)
463	text.Overlined = n.Style["text-decoration"] == "overline"
464	text.Underlined = n.Style["text-decoration"] == "underline"
465	text.LineThrough = n.Style["text-decoration"] == "linethrough"
466	text.EM = int(self.EM)
467	text.Width = int(parent.Width)
468	text.Text = n.InnerText
469
470	if n.Style["word-spacing"] == "" {
471		text.WordSpacing = font.MeasureSpace(&text)
472	}
473
474	img, width := font.Render(&text)
475	self.Texture = img
476
477	if n.Style["height"] == "" {
478		self.Height = float32(text.LineHeight)
479	}
480
481	if n.Style["width"] == "" {
482		self.Width = float32(width)
483	}
484
485	return self
486}