devicescale.go (1649B)
1 // Copyright 2018 The Ebiten Authors 2 // 3 // Licensed under the Apache License, Version 2.0 (the "License"); 4 // you may not use this file except in compliance with the License. 5 // You may obtain a copy of the License at 6 // 7 // http://www.apache.org/licenses/LICENSE-2.0 8 // 9 // Unless required by applicable law or agreed to in writing, software 10 // distributed under the License is distributed on an "AS IS" BASIS, 11 // WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied. 12 // See the License for the specific language governing permissions and 13 // limitations under the License. 14 15 package devicescale 16 17 import ( 18 "sync" 19 ) 20 21 type pos struct { 22 x, y int 23 } 24 25 var ( 26 m sync.Mutex 27 cache = map[pos]float64{} 28 ) 29 30 // GetAt returns the device scale at (x, y), i.e. the number of device-dependent pixels per device-independent pixel. 31 // x and y are in device-dependent pixels and must be the top-left coordinate of a monitor, or 0,0 to request a "global scale". 32 func GetAt(x, y int) float64 { 33 m.Lock() 34 defer m.Unlock() 35 if s, ok := cache[pos{x, y}]; ok { 36 return s 37 } 38 s := impl(x, y) 39 cache[pos{x, y}] = s 40 return s 41 } 42 43 // CelarCache clears the cache. 44 // This should be called when monitors are changed by connecting or disconnecting. 45 func ClearCache() { 46 // TODO: This should be called not only when monitors are changed but also a monitor's scales are changed. 47 // The device scale can vary even for the same monitor. 48 // The only known case is when the application works on macOS, with OpenGL, with a wider screen mode, 49 // and in the fullscreen mode (#1573). 50 51 m.Lock() 52 defer m.Unlock() 53 for k := range cache { 54 delete(cache, k) 55 } 56 }