From eb054031d2a8979f2683527ace978bb0034e12a0 Mon Sep 17 00:00:00 2001
From: Waleed Khaled <waleed1kh@outlook.com>
Date: Mon, 5 Sep 2022 18:02:50 +0400
Subject: [PATCH] fix(useDevicePixelRatio): more efficient mechanism (#2044)

Co-authored-by: Anthony Fu <anthonyfu117@hotmail.com>
---
 packages/core/useDevicePixelRatio/demo.vue |  1 +
 packages/core/useDevicePixelRatio/index.md |  2 +-
 packages/core/useDevicePixelRatio/index.ts | 53 +++++++++-------------
 3 files changed, 23 insertions(+), 33 deletions(-)

diff --git a/packages/core/useDevicePixelRatio/demo.vue b/packages/core/useDevicePixelRatio/demo.vue
index 5e369a57651..fe8e8917801 100644
--- a/packages/core/useDevicePixelRatio/demo.vue
+++ b/packages/core/useDevicePixelRatio/demo.vue
@@ -10,4 +10,5 @@ const code = stringify(pixelRatio)
 <template>
   <div>Device Pixel Ratio:</div>
   <pre>{{ code }}</pre>
+  <span class="opacity-50">Zoom in and out (or move the window to a screen with a different scaling factor) to see the value changes</span>
 </template>
diff --git a/packages/core/useDevicePixelRatio/index.md b/packages/core/useDevicePixelRatio/index.md
index 1dc274689be..c7aaadb50b0 100644
--- a/packages/core/useDevicePixelRatio/index.md
+++ b/packages/core/useDevicePixelRatio/index.md
@@ -6,7 +6,7 @@ category: Sensors
 
 Reactively track [`window.devicePixelRatio`](https://developer.mozilla.org/ru/docs/Web/API/Window/devicePixelRatio)
 >
-> NOTE: there is no event listener for `window.devicePixelRatio` change. So this function uses [`Testing media queries programmatically (window.matchMedia)`](https://developer.mozilla.org/en-US/docs/Web/CSS/Media_Queries/Testing_media_queries) as described in [this example](https://stackoverflow.com/questions/28905420/window-devicepixelratio-change-listener/29653772#29653772), but unlike the example this function subscribes to **several** pixelRatio scales (taken from [mydevice.io](https://www.mydevice.io/)) to detect any `window.devicePixelRatio` change.
+> NOTE: there is no event listener for `window.devicePixelRatio` change. So this function uses [`Testing media queries programmatically (window.matchMedia)`](https://developer.mozilla.org/en-US/docs/Web/CSS/Media_Queries/Testing_media_queries) applying the same mechanism as described in [this example](https://developer.mozilla.org/en-US/docs/Web/API/Window/devicePixelRatio#monitoring_screen_resolution_or_zoom_level_changes).
 
 ## Usage
 
diff --git a/packages/core/useDevicePixelRatio/index.ts b/packages/core/useDevicePixelRatio/index.ts
index b93b2523bb6..b0e6f596864 100644
--- a/packages/core/useDevicePixelRatio/index.ts
+++ b/packages/core/useDevicePixelRatio/index.ts
@@ -1,24 +1,7 @@
-import { ref, watch } from 'vue-demi'
-import { useEventListener } from '../useEventListener'
-import { useMediaQuery } from '../useMediaQuery'
-import type { ConfigurableWindow } from '../_configurable'
-import { defaultWindow } from '../_configurable'
-
-// device pixel ratio statistics from https://www.mydevice.io/
-const DEVICE_PIXEL_RATIO_SCALES = [
-  1,
-  1.325,
-  1.4,
-  1.5,
-  1.8,
-  2,
-  2.4,
-  2.5,
-  2.75,
-  3,
-  3.5,
-  4,
-]
+import { ref } from 'vue-demi'
+import { type Fn, tryOnScopeDispose } from '@vueuse/shared'
+import { type ConfigurableWindow, defaultWindow } from '../_configurable'
+
 /**
  * Reactively track `window.devicePixelRatio`.
  *
@@ -34,21 +17,27 @@ export function useDevicePixelRatio({
     }
   }
 
-  const pixelRatio = ref(window.devicePixelRatio)
+  const pixelRatio = ref(1)
 
-  const handleDevicePixelRatio = () => {
-    pixelRatio.value = window.devicePixelRatio
-  }
+  const cleanups: Fn[] = []
 
-  useEventListener(window, 'resize', handleDevicePixelRatio, { passive: true })
+  const cleanup = () => {
+    cleanups.map(i => i())
+    cleanups.length = 0
+  }
 
-  DEVICE_PIXEL_RATIO_SCALES.forEach((dppx) => {
-    // listen mql events in both sides
-    const mqlMin = useMediaQuery(`screen and (min-resolution: ${dppx}dppx)`)
-    const mqlMax = useMediaQuery(`screen and (max-resolution: ${dppx}dppx)`)
+  const observe = () => {
+    pixelRatio.value = window.devicePixelRatio
+    cleanup()
+    const media = window.matchMedia(`(resolution: ${pixelRatio.value}dppx)`)
+    media.addEventListener('change', observe, { once: true })
+    cleanups.push(() => {
+      media.removeEventListener('change', observe)
+    })
+  }
 
-    watch([mqlMin, mqlMax], handleDevicePixelRatio)
-  })
+  observe()
+  tryOnScopeDispose(cleanup)
 
   return { pixelRatio }
 }