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1 import { chrome, chrome_version, gecko, ie, mac, presto, safari, webkit } from "../util/browser.js"
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2 import { e_preventDefault } from "../util/event.js"
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3
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4 import { updateDisplaySimple } from "./update_display.js"
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5 import { setScrollLeft, updateScrollTop } from "./scrolling.js"
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6
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7 // Since the delta values reported on mouse wheel events are
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8 // unstandardized between browsers and even browser versions, and
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9 // generally horribly unpredictable, this code starts by measuring
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10 // the scroll effect that the first few mouse wheel events have,
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11 // and, from that, detects the way it can convert deltas to pixel
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12 // offsets afterwards.
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13 //
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14 // The reason we want to know the amount a wheel event will scroll
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15 // is that it gives us a chance to update the display before the
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16 // actual scrolling happens, reducing flickering.
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17
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18 let wheelSamples = 0, wheelPixelsPerUnit = null
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19 // Fill in a browser-detected starting value on browsers where we
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20 // know one. These don't have to be accurate -- the result of them
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21 // being wrong would just be a slight flicker on the first wheel
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22 // scroll (if it is large enough).
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23 if (ie) wheelPixelsPerUnit = -.53
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24 else if (gecko) wheelPixelsPerUnit = 15
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25 else if (chrome) wheelPixelsPerUnit = -.7
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26 else if (safari) wheelPixelsPerUnit = -1/3
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27
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28 function wheelEventDelta(e) {
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29 let dx = e.wheelDeltaX, dy = e.wheelDeltaY
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30 if (dx == null && e.detail && e.axis == e.HORIZONTAL_AXIS) dx = e.detail
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31 if (dy == null && e.detail && e.axis == e.VERTICAL_AXIS) dy = e.detail
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32 else if (dy == null) dy = e.wheelDelta
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33 return {x: dx, y: dy}
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34 }
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35 export function wheelEventPixels(e) {
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36 let delta = wheelEventDelta(e)
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37 delta.x *= wheelPixelsPerUnit
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38 delta.y *= wheelPixelsPerUnit
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39 return delta
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40 }
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41
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42 export function onScrollWheel(cm, e) {
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43 // On Chrome 102, viewport updates somehow stop wheel-based
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44 // scrolling. Turning off pointer events during the scroll seems
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45 // to avoid the issue.
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46 if (chrome && chrome_version == 102) {
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47 if (cm.display.chromeScrollHack == null) cm.display.sizer.style.pointerEvents = "none"
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48 else clearTimeout(cm.display.chromeScrollHack)
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49 cm.display.chromeScrollHack = setTimeout(() => {
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50 cm.display.chromeScrollHack = null
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51 cm.display.sizer.style.pointerEvents = ""
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52 }, 100)
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53 }
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54 let delta = wheelEventDelta(e), dx = delta.x, dy = delta.y
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55 let pixelsPerUnit = wheelPixelsPerUnit
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56 if (e.deltaMode === 0) {
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57 dx = e.deltaX
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58 dy = e.deltaY
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59 pixelsPerUnit = 1
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60 }
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61
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62 let display = cm.display, scroll = display.scroller
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63 // Quit if there's nothing to scroll here
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64 let canScrollX = scroll.scrollWidth > scroll.clientWidth
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65 let canScrollY = scroll.scrollHeight > scroll.clientHeight
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66 if (!(dx && canScrollX || dy && canScrollY)) return
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67
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68 // Webkit browsers on OS X abort momentum scrolls when the target
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69 // of the scroll event is removed from the scrollable element.
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70 // This hack (see related code in patchDisplay) makes sure the
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71 // element is kept around.
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72 if (dy && mac && webkit) {
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73 outer: for (let cur = e.target, view = display.view; cur != scroll; cur = cur.parentNode) {
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74 for (let i = 0; i < view.length; i++) {
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75 if (view[i].node == cur) {
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76 cm.display.currentWheelTarget = cur
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77 break outer
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78 }
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79 }
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80 }
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81 }
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82
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83 // On some browsers, horizontal scrolling will cause redraws to
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84 // happen before the gutter has been realigned, causing it to
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85 // wriggle around in a most unseemly way. When we have an
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86 // estimated pixels/delta value, we just handle horizontal
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87 // scrolling entirely here. It'll be slightly off from native, but
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88 // better than glitching out.
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89 if (dx && !gecko && !presto && pixelsPerUnit != null) {
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90 if (dy && canScrollY)
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91 updateScrollTop(cm, Math.max(0, scroll.scrollTop + dy * pixelsPerUnit))
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92 setScrollLeft(cm, Math.max(0, scroll.scrollLeft + dx * pixelsPerUnit))
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93 // Only prevent default scrolling if vertical scrolling is
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94 // actually possible. Otherwise, it causes vertical scroll
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95 // jitter on OSX trackpads when deltaX is small and deltaY
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96 // is large (issue #3579)
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97 if (!dy || (dy && canScrollY))
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98 e_preventDefault(e)
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99 display.wheelStartX = null // Abort measurement, if in progress
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100 return
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101 }
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102
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103 // 'Project' the visible viewport to cover the area that is being
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104 // scrolled into view (if we know enough to estimate it).
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105 if (dy && pixelsPerUnit != null) {
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106 let pixels = dy * pixelsPerUnit
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107 let top = cm.doc.scrollTop, bot = top + display.wrapper.clientHeight
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108 if (pixels < 0) top = Math.max(0, top + pixels - 50)
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109 else bot = Math.min(cm.doc.height, bot + pixels + 50)
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110 updateDisplaySimple(cm, {top: top, bottom: bot})
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111 }
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112
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113 if (wheelSamples < 20 && e.deltaMode !== 0) {
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114 if (display.wheelStartX == null) {
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115 display.wheelStartX = scroll.scrollLeft; display.wheelStartY = scroll.scrollTop
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116 display.wheelDX = dx; display.wheelDY = dy
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117 setTimeout(() => {
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118 if (display.wheelStartX == null) return
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119 let movedX = scroll.scrollLeft - display.wheelStartX
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120 let movedY = scroll.scrollTop - display.wheelStartY
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121 let sample = (movedY && display.wheelDY && movedY / display.wheelDY) ||
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122 (movedX && display.wheelDX && movedX / display.wheelDX)
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123 display.wheelStartX = display.wheelStartY = null
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124 if (!sample) return
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125 wheelPixelsPerUnit = (wheelPixelsPerUnit * wheelSamples + sample) / (wheelSamples + 1)
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126 ++wheelSamples
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127 }, 200)
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128 } else {
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129 display.wheelDX += dx; display.wheelDY += dy
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130 }
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131 }
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132 }
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