add image capturing for linux

Overlord-Client/cmd/agent/capture/capture_linux.go

@@ -4,10 +4,18 @@ package capture
 
 import (
 	"image"
+
+	"github.com/kbinani/screenshot"
 )
 
-var activeDisplays = func() int { return 0 }
+var activeDisplays = func() int {
+	return screenshot.NumActiveDisplays()
+}
 
-var captureDisplayFn = func(int) (*image.RGBA, error) { return nil, nil }
+var captureDisplayFn = func(display int) (*image.RGBA, error) {
+	return screenshot.CaptureDisplay(display)
+}
 
-func displayCount() int { return 0 }
+func displayCount() int {
+	return screenshot.NumActiveDisplays()
+}

Overlord-Client/cmd/agent/capture/monitors_linux.go

@@ -0,0 +1,30 @@
+//go:build linux
+
+package capture
+
+import (
+	"image"
+
+	"github.com/kbinani/screenshot"
+)
+
+func displayBounds(idx int) image.Rectangle {
+	return screenshot.GetDisplayBounds(idx)
+}
+
+func displayScale(idx int) float64 {
+	return 1.0
+}
+
+func MonitorInfos() []MonitorInfo {
+	n := screenshot.NumActiveDisplays()
+	infos := make([]MonitorInfo, 0, n)
+	for i := 0; i < n; i++ {
+		b := screenshot.GetDisplayBounds(i)
+		infos = append(infos, MonitorInfo{
+			Width:  b.Dx(),
+			Height: b.Dy(),
+		})
+	}
+	return infos
+}

Overlord-Client/cmd/agent/capture/monitors_stub.go

@@ -1,4 +1,4 @@
-//go:build !windows
+//go:build !windows && !linux
 
 package capture