Fixed X11 behavior when disconnecting / connecting the last display

- Removed the one-time detection of headless display
- Removed virtual "Display" display created when no monitor is plugged
- Hardened monitor functions

src/x11_init.c

@@ -499,31 +499,6 @@ static GLFWbool initExtensions(void)
 
     if (_glfw.x11.randr.available)
     {
-        XRRScreenResources* sr = XRRGetScreenResourcesCurrent(_glfw.x11.display,
-                                                              _glfw.x11.root);
-
-        if (!sr->ncrtc || !XRRGetCrtcGammaSize(_glfw.x11.display, sr->crtcs[0]))
-        {
-            // This is either a headless system or an older Nvidia binary driver
-            // with broken gamma support
-            // Flag it as useless and fall back to Xf86VidMode gamma, if
-            // available
-            _glfwInputError(GLFW_PLATFORM_ERROR,
-                            "X11: Detected broken RandR gamma ramp support");
-            _glfw.x11.randr.gammaBroken = GLFW_TRUE;
-        }
-
-        if (!sr->ncrtc || !sr->noutput || !sr->nmode)
-        {
-            // This is either a headless system or broken Cygwin/X RandR
-            // Flag it as useless and fall back to Xlib display functions
-            _glfwInputError(GLFW_PLATFORM_ERROR,
-                            "X11: Detected broken RandR monitor support");
-            _glfw.x11.randr.monitorBroken = GLFW_TRUE;
-        }
-
-        XRRFreeScreenResources(sr);
-
         XRRSelectInput(_glfw.x11.display, _glfw.x11.root,
                        RROutputChangeNotifyMask);
     }

src/x11_monitor.c

@@ -99,7 +99,7 @@ static GLFWvidmode vidmodeFromModeInfo(const XRRModeInfo* mi,
 //
 void _glfwPollMonitorsX11(void)
 {
-    if (_glfw.x11.randr.available && !_glfw.x11.randr.monitorBroken)
+    if (_glfw.x11.randr.available)
     {
         int i, j, disconnectedCount, screenCount = 0;
         _GLFWmonitor** disconnected;
@@ -199,23 +199,6 @@ void _glfwPollMonitorsX11(void)
         }
 
         free(disconnected);
-
-        if (!_glfw.monitorCount)
-        {
-            _glfwInputError(GLFW_PLATFORM_ERROR,
-                            "X11: RandR monitor support seems broken");
-            _glfw.x11.randr.monitorBroken = GLFW_TRUE;
-        }
-    }
-
-    if (!_glfw.monitorCount)
-    {
-        const int widthMM = DisplayWidthMM(_glfw.x11.display, _glfw.x11.screen);
-        const int heightMM = DisplayHeightMM(_glfw.x11.display, _glfw.x11.screen);
-
-        _glfwInputMonitor(_glfwAllocMonitor("Display", widthMM, heightMM),
-                          GLFW_CONNECTED,
-                          _GLFW_INSERT_FIRST);
     }
 }
 
@@ -223,7 +206,7 @@ void _glfwPollMonitorsX11(void)
 //
 GLFWbool _glfwSetVideoModeX11(_GLFWmonitor* monitor, const GLFWvidmode* desired)
 {
-    if (_glfw.x11.randr.available && !_glfw.x11.randr.monitorBroken)
+    if (_glfw.x11.randr.available && monitor->x11.crtc && monitor->x11.output)
     {
         XRRScreenResources* sr;
         XRRCrtcInfo* ci;
@@ -290,7 +273,7 @@ GLFWbool _glfwSetVideoModeX11(_GLFWmonitor* monitor, const GLFWvidmode* desired)
 //
 void _glfwRestoreVideoModeX11(_GLFWmonitor* monitor)
 {
-    if (_glfw.x11.randr.available && !_glfw.x11.randr.monitorBroken)
+    if (_glfw.x11.randr.available && monitor->x11.crtc)
     {
         XRRScreenResources* sr;
         XRRCrtcInfo* ci;
@@ -324,7 +307,7 @@ void _glfwRestoreVideoModeX11(_GLFWmonitor* monitor)
 
 void _glfwPlatformGetMonitorPos(_GLFWmonitor* monitor, int* xpos, int* ypos)
 {
-    if (_glfw.x11.randr.available && !_glfw.x11.randr.monitorBroken)
+    if (_glfw.x11.randr.available && monitor->x11.crtc)
     {
         XRRScreenResources* sr;
         XRRCrtcInfo* ci;
@@ -348,7 +331,9 @@ GLFWvidmode* _glfwPlatformGetVideoModes(_GLFWmonitor* monitor, int* count)
 
     *count = 0;
 
-    if (_glfw.x11.randr.available && !_glfw.x11.randr.monitorBroken)
+    if (_glfw.x11.randr.available)
+    {
+        if (monitor->x11.crtc && monitor->x11.output)
         {
             int i, j;
             XRRScreenResources* sr;
@@ -387,6 +372,7 @@ GLFWvidmode* _glfwPlatformGetVideoModes(_GLFWmonitor* monitor, int* count)
             XRRFreeCrtcInfo(ci);
             XRRFreeScreenResources(sr);
         }
+    }
     else
     {
         *count = 1;
@@ -399,7 +385,9 @@ GLFWvidmode* _glfwPlatformGetVideoModes(_GLFWmonitor* monitor, int* count)
 
 void _glfwPlatformGetVideoMode(_GLFWmonitor* monitor, GLFWvidmode* mode)
 {
-    if (_glfw.x11.randr.available && !_glfw.x11.randr.monitorBroken)
+    if (_glfw.x11.randr.available)
+    {
+        if (monitor->x11.crtc)
         {
             XRRScreenResources* sr;
             XRRCrtcInfo* ci;
@@ -412,6 +400,7 @@ void _glfwPlatformGetVideoMode(_GLFWmonitor* monitor, GLFWvidmode* mode)
             XRRFreeCrtcInfo(ci);
             XRRFreeScreenResources(sr);
         }
+    }
     else
     {
         mode->width = DisplayWidth(_glfw.x11.display, _glfw.x11.screen);
@@ -425,10 +414,14 @@ void _glfwPlatformGetVideoMode(_GLFWmonitor* monitor, GLFWvidmode* mode)
 
 void _glfwPlatformGetGammaRamp(_GLFWmonitor* monitor, GLFWgammaramp* ramp)
 {
-    if (_glfw.x11.randr.available && !_glfw.x11.randr.gammaBroken)
+    if (_glfw.x11.randr.available)
+    {
+        if (monitor->x11.crtc)
         {
             const size_t size = XRRGetCrtcGammaSize(_glfw.x11.display,
                                                     monitor->x11.crtc);
+            if (size)
+            {
               XRRCrtcGamma* gamma = XRRGetCrtcGamma(_glfw.x11.display,
                                                     monitor->x11.crtc);
 
@@ -440,6 +433,8 @@ void _glfwPlatformGetGammaRamp(_GLFWmonitor* monitor, GLFWgammaramp* ramp)
 
               XRRFreeGamma(gamma);
             }
+        }
+    }
     else if (_glfw.x11.vidmode.available)
     {
         int size;
@@ -455,7 +450,9 @@ void _glfwPlatformGetGammaRamp(_GLFWmonitor* monitor, GLFWgammaramp* ramp)
 
 void _glfwPlatformSetGammaRamp(_GLFWmonitor* monitor, const GLFWgammaramp* ramp)
 {
-    if (_glfw.x11.randr.available && !_glfw.x11.randr.gammaBroken)
+    if (_glfw.x11.randr.available)
+    {
+        if (monitor->x11.crtc)
         {
             XRRCrtcGamma* gamma = XRRAllocGamma(ramp->size);
 
@@ -466,6 +463,7 @@ void _glfwPlatformSetGammaRamp(_GLFWmonitor* monitor, const GLFWgammaramp* ramp)
             XRRSetCrtcGamma(_glfw.x11.display, monitor->x11.crtc, gamma);
             XRRFreeGamma(gamma);
         }
+    }
     else if (_glfw.x11.vidmode.available)
     {
         XF86VidModeSetGammaRamp(_glfw.x11.display,

src/x11_platform.h

@@ -221,8 +221,6 @@ typedef struct _GLFWlibraryX11
         int         errorBase;
         int         major;
         int         minor;
-        GLFWbool    gammaBroken;
-        GLFWbool    monitorBroken;
     } randr;
 
     struct {