From fd688af424be0b953f7b7d1107d07ee668655868 Mon Sep 17 00:00:00 2001
From: Simon Rettberg
Date: Tue, 22 Oct 2019 14:20:53 +0200
Subject: Improve Xlib error handling

---
 src/xprivate.cpp | 67 ++++++++++++++++++++++++++++++++++----------------------
 1 file changed, 41 insertions(+), 26 deletions(-)

diff --git a/src/xprivate.cpp b/src/xprivate.cpp
index 1273e1e..bef9471 100644
--- a/src/xprivate.cpp
+++ b/src/xprivate.cpp
@@ -3,6 +3,10 @@
 #include <QDebug>
 #include <QRegularExpression>
 
+// Put this here as we need it in the static error handler
+static Display* __display;
+static XErrorHandler old_handler;
+
 static double toVertRefresh(const XRRModeInfo *mode)
 {
     if (mode->hTotal > 0 && mode->vTotal > 0)
@@ -61,9 +65,15 @@ static int modeEqual(const XRRModeInfo *a, const XRRModeInfo *b)
 
 static int errorHandler(Display *dpy, XErrorEvent *err)
 {
-    char buf[1000];
-    XGetErrorText(dpy, err->error_code, buf, 1000);
-    qDebug() << "**X11 error**" << buf;
+    if (dpy != __display) {
+        if (old_handler != nullptr) {
+            return old_handler(dpy, err);
+        }
+    } else {
+        char buf[1000];
+        XGetErrorText(dpy, err->error_code, buf, 1000);
+        qDebug() << "**X11 error**" << buf;
+    }
     return 0;
 }
 
@@ -75,12 +85,12 @@ XPrivate::XPrivate()
     : _screenResources(nullptr)
 {
     // Get initial data (to be freed)
-    _display = XOpenDisplay(nullptr);
+    __display = _display = XOpenDisplay(nullptr);
     if (_display == nullptr) {
             qFatal("Cannot open display");
             ::exit(1);
     }
-    XSetErrorHandler(errorHandler);
+    old_handler = XSetErrorHandler(errorHandler);
     _EDID_ATOM = XInternAtom(_display, RR_PROPERTY_RANDR_EDID, False);
 }
 
@@ -120,7 +130,7 @@ void XPrivate::updateScreenResources()
     freeResources();
     _screenResources = XRRGetScreenResourcesCurrent(_display, DefaultRootWindow(_display));
     // Create the modemap
-    qDebug() << "Modes";
+    qDebug() << "updateScreenResources: Modes";
     for (int i = 0; i < _screenResources->nmode; ++i) {
             _modeMap.insert(
                                     _screenResources->modes[i].id,
@@ -145,7 +155,7 @@ void XPrivate::updateScreenResources()
     */
 
     // Create crtcMap
-    qDebug() << "CRTCs";
+    qDebug() << "updateScreenResources: CRTCs";
     for (int i = 0; i < _screenResources->ncrtc; ++i) {
             XRRCrtcInfo * info = XRRGetCrtcInfo(
                                     _display,
@@ -160,7 +170,7 @@ void XPrivate::updateScreenResources()
     }
 
     // Create outputmap and connectedOutputMap
-    qDebug() << "Outputs";
+    qDebug() << "updateScreenResources: Outputs";
     QHash<RROutput, QString> tempMap;
     QMap<Projector, int> typeCount;
     for (int i = 0; i < _screenResources->noutput; ++i) {
@@ -234,7 +244,7 @@ void XPrivate::updateScreenResources()
             return;
     qSort(screens.begin(), screens.end(), xRectLessThan);
     int endX = -0xffff;
-    qDebug() << "From left to right";
+    qDebug() << "updateScreenResources: From left to right";
 	for (OutputInfo* output : screens) {
 		if (output->mode == nullptr) {
 			qDebug() << "(Ignoring" << output->outputName << "since it's disconnected)";
@@ -252,33 +262,37 @@ void XPrivate::updateScreenResources()
 			endX = output->crtc->x + int(output->mode->width);
 		}
 	}
-    qDebug() << "Loaded.";
+    qDebug() << "updateScreenResources: Loaded.";
 }
 
 void XPrivate::addMissingEdidResolutions()
 {
-	XRRScreenResources *resptr = XRRGetScreenResourcesCurrent(_display, DefaultRootWindow(_display));
-	for (int i = 0; i < resptr->noutput; ++i) {
-		unsigned char prop[512];
-		unsigned long edidLen = 512;
-		if (!getEdid(resptr->outputs[i], prop, &edidLen))
-			continue;
-		if (edidLen < 128)
-			continue;
-		for (unsigned int j = 54; j < 125; j+= 18) {
-			addMissingModesFromDtd(resptr, resptr->outputs[i], prop + j);
-		}
-		for (unsigned int j = 128; j < edidLen - 127; j += 128) {
-			addMissingModesFromExtBlock(resptr, resptr->outputs[i], prop + j);
-		}
-	}
-	XRRFreeScreenResources(resptr);
+    qDebug() << "addMissingEdidResolutions";
+    XRRScreenResources *resptr = XRRGetScreenResourcesCurrent(_display, DefaultRootWindow(_display));
+    if (resptr == nullptr)
+        return;
+    for (int i = 0; i < resptr->noutput; ++i) {
+        unsigned char prop[512];
+        unsigned long edidLen = 512;
+        if (!getEdid(resptr->outputs[i], prop, &edidLen))
+            continue;
+        if (edidLen < 128)
+            continue;
+        for (unsigned int j = 54; j < 125; j+= 18) {
+            addMissingModesFromDtd(resptr, resptr->outputs[i], prop + j);
+        }
+        for (unsigned int j = 128; j < edidLen - 127; j += 128) {
+            addMissingModesFromExtBlock(resptr, resptr->outputs[i], prop + j);
+        }
+    }
+    XRRFreeScreenResources(resptr);
 }
 
 bool XPrivate::getEdid(RROutput outputId, unsigned char *buffer, unsigned long *size)
 {
 	int numProps = 0;
 	bool found = false;
+    qDebug() << "getEdid:" << outputId;
 	Atom* properties = XRRListOutputProperties(_display, outputId, &numProps);
 	for (int i = 0; i < numProps; ++i) {
 		if (properties[i] == _EDID_ATOM) {
@@ -351,6 +365,7 @@ void XPrivate::addMissingModesFromExtBlock(XRRScreenResources *res, RROutput out
 		dtdOffset = 128;
 	}
 
+    qDebug() << "addMissingModesFromExtBlock:" << outputId;
 	for (int i = dtdOffset; i < 128 - 17; i += 18) {
 		addMissingModesFromDtd(res, outputId, data + i);
 	}
-- 
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