[x11] [multimon] feature: find the screen a window is on

Introduce parity to X11 from Windows. Respect per-monitor bounds.

Author: ajerick

os/x11/monitor.cpp

@@ -1,6 +1,12 @@
-#include "monitor.h"
+#include "os/x11/monitor.h"
+#include "gfx/rect.h"
+#include "os/ref.h"
+#include "os/screen.h"
 #include "os/x11/x11.h"
+#include "os/x11/screen.h"
 
+#include <climits>
+#include <algorithm>
 #include <X11/extensions/Xrandr.h>
 
 namespace os {
@@ -18,7 +24,43 @@ MonitorsX11::MonitorsX11()
 
 int MonitorsX11::numMonitors() const { return m_numMonitors; }
 
-const XRRMonitorInfo& MonitorsX11::monitor(int monitorNum) const { return m_monitors.get()[monitorNum]; }
+const XRRMonitorInfo& MonitorsX11::monitorInfo(int monitorNum) const { return m_monitors.get()[monitorNum]; }
+
+// searches for the monitor containing the most area of the window
+ScreenRef MonitorsX11::nearestMonitorOf(const gfx::Rect& frame) const
+{
+  ScreenRef candidate = nullptr;
+  int most_area = INT_MIN;
+
+  for (int nmonitor=0; nmonitor<m_numMonitors; nmonitor++) {
+    ScreenRef monitor = os::make_ref<ScreenX11>(nmonitor);
+
+    const gfx::Rect& bounds = monitor->bounds();
+    gfx::Rect segment(frame);
+    if (segment.x < bounds.x) {
+      segment.w = std::max(0, segment.w - (bounds.x-segment.x));
+      segment.x = bounds.x;
+    }
+    if (segment.x2() > bounds.x2()) {
+      segment.w = std::max(0, segment.w - (segment.x2()-bounds.x2()));
+    }
+    if (segment.y < bounds.y) {
+      segment.h = std::max(0, segment.h - (bounds.y-segment.y));
+      segment.y = bounds.y;
+    }
+    if (segment.y2() > bounds.y2()) {
+      segment.h = std::max(0, segment.h - (segment.y2()-bounds.y2()));
+    }
+
+    int area = segment.w*segment.h;
+    if (area > most_area) {
+      candidate = monitor;
+      most_area = area;
+    }
+  }
+
+  return candidate;
+}
 
 } // namespace os
 

os/x11/monitor.h

@@ -2,8 +2,11 @@
 #define MONITOR_H
 #pragma once
 
-#include <memory>
+#include "gfx/fwd.h"
+#include "os/screen.h"
+
 #include <X11/extensions/Xrandr.h>
+#include <memory>
 
 namespace os {
 
@@ -16,8 +19,11 @@ typedef std::unique_ptr<XRRMonitorInfo, MonitorCloser> unique_monitors_ptr;
 class MonitorsX11 {
 public:
   MonitorsX11();
+
   int numMonitors() const;
-  const XRRMonitorInfo& monitor(int monitorNum) const;
+  const XRRMonitorInfo& monitorInfo(int monitorNum) const;
+
+  ScreenRef nearestMonitorOf(const gfx::Rect& frame) const;
 
 private:
   int m_numMonitors;

os/x11/screen.h

@@ -11,6 +11,7 @@
 #include "os/screen.h"
 #include "os/x11/monitor.h"
 #include "os/x11/x11.h"
+#include "os/system.h"
 
 #include <X11/extensions/Xrandr.h>
 
@@ -20,7 +21,7 @@ class ScreenX11 : public Screen {
 public:
   ScreenX11(int monitorNum) : m_monitorNum(monitorNum) {
     MonitorsX11* monitors = X11::instance()->monitors();
-    const XRRMonitorInfo& monitor = monitors->monitor(monitorNum);
+    const XRRMonitorInfo& monitor = monitors->monitorInfo(monitorNum);
 
     m_bounds.x = monitor.x;
     m_bounds.y = monitor.y;

os/x11/system.h

@@ -89,7 +89,7 @@ class SystemX11 : public CommonSystem {
 
     // we have to search for the primary monitor
     for (int monitor=0; monitor<numMonitors; monitor++) {
-      if (monitors->monitor(monitor).primary) {
+      if (monitors->monitorInfo(monitor).primary) {
         return make_ref<ScreenX11>(monitor);
       }
     }

os/x11/window.cpp

@@ -447,7 +447,11 @@ WindowX11::~WindowX11()
 
 os::ScreenRef WindowX11::screen() const
 {
-  return os::instance()->mainScreen();
+  ScreenRef nearestMonitor = X11::instance()->monitors()->nearestMonitorOf(frame());
+  if (nearestMonitor)
+    return nearestMonitor;
+  else
+    return os::instance()->mainScreen();
 }
 
 os::ColorSpaceRef WindowX11::colorSpace() const