gemini-browser

cell.go (6807B)

---

 // Copyright 2024 The TCell Authors
 //
 // Licensed under the Apache License, Version 2.0 (the "License");
 // you may not use file except in compliance with the License.
 // You may obtain a copy of the license at
 //
 //    http://www.apache.org/licenses/LICENSE-2.0
 //
 // Unless required by applicable law or agreed to in writing, software
 // distributed under the License is distributed on an "AS IS" BASIS,
 // WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
 // See the License for the specific language governing permissions and
 // limitations under the License.
 
 package tcell
 
 import (
 	"os"
 	"reflect"
 
 	runewidth "github.com/mattn/go-runewidth"
 )
 
 type cell struct {
 	currMain  rune
 	currComb  []rune
 	currStyle Style
 	lastMain  rune
 	lastStyle Style
 	lastComb  []rune
 	width     int
 	lock      bool
 }
 
 // CellBuffer represents a two-dimensional array of character cells.
 // This is primarily intended for use by Screen implementors; it
 // contains much of the common code they need.  To create one, just
 // declare a variable of its type; no explicit initialization is necessary.
 //
 // CellBuffer is not thread safe.
 type CellBuffer struct {
 	w     int
 	h     int
 	cells []cell
 }
 
 // SetContent sets the contents (primary rune, combining runes,
 // and style) for a cell at a given location.  If the background or
 // foreground of the style is set to ColorNone, then the respective
 // color is left un changed.
 func (cb *CellBuffer) SetContent(x int, y int,
 	mainc rune, combc []rune, style Style,
 ) {
 	if x >= 0 && y >= 0 && x < cb.w && y < cb.h {
 		c := &cb.cells[(y*cb.w)+x]
 
 		// Wide characters: we want to mark the "wide" cells
 		// dirty as well as the base cell, to make sure we consider
 		// both cells as dirty together.  We only need to do this
 		// if we're changing content
 		if (c.width > 0) && (mainc != c.currMain || len(combc) != len(c.currComb) || (len(combc) > 0 && !reflect.DeepEqual(combc, c.currComb))) {
 			for i := 0; i < c.width; i++ {
 				cb.SetDirty(x+i, y, true)
 			}
 		}
 
 		c.currComb = append([]rune{}, combc...)
 
 		if c.currMain != mainc {
 			c.width = runewidth.RuneWidth(mainc)
 		}
 		c.currMain = mainc
 		if style.fg == ColorNone {
 			style.fg = c.currStyle.fg
 		}
 		if style.bg == ColorNone {
 			style.bg = c.currStyle.bg
 		}
 		c.currStyle = style
 	}
 }
 
 // GetContent returns the contents of a character cell, including the
 // primary rune, any combining character runes (which will usually be
 // nil), the style, and the display width in cells.  (The width can be
 // either 1, normally, or 2 for East Asian full-width characters.)
 func (cb *CellBuffer) GetContent(x, y int) (rune, []rune, Style, int) {
 	var mainc rune
 	var combc []rune
 	var style Style
 	var width int
 	if x >= 0 && y >= 0 && x < cb.w && y < cb.h {
 		c := &cb.cells[(y*cb.w)+x]
 		mainc, combc, style = c.currMain, c.currComb, c.currStyle
 		if width = c.width; width == 0 || mainc < ' ' {
 			width = 1
 			mainc = ' '
 		}
 	}
 	return mainc, combc, style, width
 }
 
 // Size returns the (width, height) in cells of the buffer.
 func (cb *CellBuffer) Size() (int, int) {
 	return cb.w, cb.h
 }
 
 // Invalidate marks all characters within the buffer as dirty.
 func (cb *CellBuffer) Invalidate() {
 	for i := range cb.cells {
 		cb.cells[i].lastMain = rune(0)
 	}
 }
 
 // Dirty checks if a character at the given location needs to be
 // refreshed on the physical display.  This returns true if the cell
 // content is different since the last time it was marked clean.
 func (cb *CellBuffer) Dirty(x, y int) bool {
 	if x >= 0 && y >= 0 && x < cb.w && y < cb.h {
 		c := &cb.cells[(y*cb.w)+x]
 		if c.lock {
 			return false
 		}
 		if c.lastMain == rune(0) {
 			return true
 		}
 		if c.lastMain != c.currMain {
 			return true
 		}
 		if c.lastStyle != c.currStyle {
 			return true
 		}
 		if len(c.lastComb) != len(c.currComb) {
 			return true
 		}
 		for i := range c.lastComb {
 			if c.lastComb[i] != c.currComb[i] {
 				return true
 			}
 		}
 	}
 	return false
 }
 
 // SetDirty is normally used to indicate that a cell has
 // been displayed (in which case dirty is false), or to manually
 // force a cell to be marked dirty.
 func (cb *CellBuffer) SetDirty(x, y int, dirty bool) {
 	if x >= 0 && y >= 0 && x < cb.w && y < cb.h {
 		c := &cb.cells[(y*cb.w)+x]
 		if dirty {
 			c.lastMain = rune(0)
 		} else {
 			if c.currMain == rune(0) {
 				c.currMain = ' '
 			}
 			c.lastMain = c.currMain
 			c.lastComb = c.currComb
 			c.lastStyle = c.currStyle
 		}
 	}
 }
 
 // LockCell locks a cell from being drawn, effectively marking it "clean" until
 // the lock is removed. This can be used to prevent tcell from drawing a given
 // cell, even if the underlying content has changed. For example, when drawing a
 // sixel graphic directly to a TTY screen an implementer must lock the region
 // underneath the graphic to prevent tcell from drawing on top of the graphic.
 func (cb *CellBuffer) LockCell(x, y int) {
 	if x < 0 || y < 0 {
 		return
 	}
 	if x >= cb.w || y >= cb.h {
 		return
 	}
 	c := &cb.cells[(y*cb.w)+x]
 	c.lock = true
 }
 
 // UnlockCell removes a lock from the cell and marks it as dirty
 func (cb *CellBuffer) UnlockCell(x, y int) {
 	if x < 0 || y < 0 {
 		return
 	}
 	if x >= cb.w || y >= cb.h {
 		return
 	}
 	c := &cb.cells[(y*cb.w)+x]
 	c.lock = false
 	cb.SetDirty(x, y, true)
 }
 
 // Resize is used to resize the cells array, with different dimensions,
 // while preserving the original contents.  The cells will be invalidated
 // so that they can be redrawn.
 func (cb *CellBuffer) Resize(w, h int) {
 	if cb.h == h && cb.w == w {
 		return
 	}
 
 	newc := make([]cell, w*h)
 	for y := 0; y < h && y < cb.h; y++ {
 		for x := 0; x < w && x < cb.w; x++ {
 			oc := &cb.cells[(y*cb.w)+x]
 			nc := &newc[(y*w)+x]
 			nc.currMain = oc.currMain
 			nc.currComb = oc.currComb
 			nc.currStyle = oc.currStyle
 			nc.width = oc.width
 			nc.lastMain = rune(0)
 		}
 	}
 	cb.cells = newc
 	cb.h = h
 	cb.w = w
 }
 
 // Fill fills the entire cell buffer array with the specified character
 // and style.  Normally choose ' ' to clear the screen.  This API doesn't
 // support combining characters, or characters with a width larger than one.
 // If either the foreground or background are ColorNone, then the respective
 // color is unchanged.
 func (cb *CellBuffer) Fill(r rune, style Style) {
 	for i := range cb.cells {
 		c := &cb.cells[i]
 		c.currMain = r
 		c.currComb = nil
 		cs := style
 		if cs.fg == ColorNone {
 			cs.fg = c.currStyle.fg
 		}
 		if cs.bg == ColorNone {
 			cs.bg = c.currStyle.bg
 		}
 		c.currStyle = cs
 		c.width = 1
 	}
 }
 
 var runeConfig *runewidth.Condition
 
 func init() {
 	// The defaults for the runewidth package are poorly chosen for terminal
 	// applications.  We however will honor the setting in the environment if
 	// it is set.
 	if os.Getenv("RUNEWIDTH_EASTASIAN") == "" {
 		runewidth.DefaultCondition.EastAsianWidth = false
 	}
 }