ebiten/internal/devicescale/devicescale.go

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// Copyright 2018 The Ebiten Authors
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//
// Licensed under the Apache License, Version 2.0 (the "License");
// you may not use this 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.
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package devicescale
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import (
"sync"
)
type posAndScale struct {
x, y int
scale float64
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}
var (
m sync.Mutex
cache []posAndScale
)
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// GetAt returns the device scale at (x, y), i.e. the number of device-dependent pixels per device-independent pixel.
// 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".
func GetAt(x, y int) float64 {
m.Lock()
defer m.Unlock()
for _, p := range cache {
if p.x == x && p.y == y {
return p.scale
}
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}
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s := impl(x, y)
cache = append(cache, posAndScale{
x: x,
y: y,
scale: s,
})
return s
}
// ClearCache clears the cache.
// This should be called when monitors are changed by connecting or disconnecting.
func ClearCache() {
// TODO: This should be called not only when monitors are changed but also a monitor's scales are changed.
// The device scale can vary even for the same monitor.
// The only known case is when the application works on macOS, with OpenGL, with a wider screen mode,
// and in the fullscreen mode (#1573).
m.Lock()
defer m.Unlock()
cache = cache[:0]
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}