qemu: command: Fix building of the SDL display command line

QEMU uses a shorthand '-sdl' which maps to '-display sdl'. However, if
there are any options to be passed to SDL, the full command version must
be used. Everything seemingly worked for us until commit 5038b30043
introduced OpenGL support for SDL and added ',gl=on/off' option which as
mentioned above could have never worked with the shorthand version of
the command. Indeed starting a domain with an SDL display and OpenGL
enabled, QEMU produces a rather cryptic error:

-sdl: Could not open 'gl=on': No such file or directory

This patch provides fixes to both the SDL cmdline generation and the
test suite.

Signed-off-by: Erik Skultety <eskultet@redhat.com>
Reviewed-by: John Ferlan <jferlan@redhat.com>

src/qemu/qemu_command.c

@@ -7765,7 +7765,6 @@ qemuBuildGraphicsSDLCommandLine(virQEMUDriverConfigPtr cfg ATTRIBUTE_UNUSED,
 {
     int ret = -1;
     virBuffer opt = VIR_BUFFER_INITIALIZER;
-    const char *optContent;
 
     if (graphics->data.sdl.xauth)
         virCommandAddEnvPair(cmd, "XAUTHORITY", graphics->data.sdl.xauth);
@@ -7781,22 +7780,26 @@ qemuBuildGraphicsSDLCommandLine(virQEMUDriverConfigPtr cfg ATTRIBUTE_UNUSED,
     virCommandAddEnvPassBlockSUID(cmd, "QEMU_AUDIO_DRV", NULL);
     virCommandAddEnvPassBlockSUID(cmd, "SDL_AUDIODRIVER", NULL);
 
-    virCommandAddArg(cmd, "-sdl");
+    virCommandAddArg(cmd, "-display");
+    virBufferAddLit(&opt, "sdl");
 
-    if (graphics->data.sdl.gl == VIR_TRISTATE_BOOL_YES) {
+    if (graphics->data.sdl.gl != VIR_TRISTATE_BOOL_ABSENT) {
         if (!virQEMUCapsGet(qemuCaps, QEMU_CAPS_SDL_GL)) {
             virReportError(VIR_ERR_CONFIG_UNSUPPORTED, "%s",
-                           _("This QEMU doesn't support SDL OpenGL"));
+                           _("OpenGL for SDL is not supported with this QEMU "
+                             "binary"));
             goto cleanup;
         }
 
-        virBufferAsprintf(&opt, "gl=%s",
+        virBufferAsprintf(&opt, ",gl=%s",
                           virTristateSwitchTypeToString(graphics->data.sdl.gl));
+
     }
 
-    optContent = virBufferCurrentContent(&opt);
-    if (optContent && STRNEQ(optContent, ""))
-        virCommandAddArgBuffer(cmd, &opt);
+    if (virBufferCheckError(&opt) < 0)
+        goto cleanup;
+
+    virCommandAddArgBuffer(cmd, &opt);
 
     ret = 0;
  cleanup:

tests/qemuxml2argvdata/graphics-sdl-fullscreen.args

@@ -25,5 +25,5 @@ server,nowait \
 -drive file=/dev/HostVG/QEMUGuest1,format=raw,if=none,id=drive-ide0-0-0 \
 -device ide-drive,bus=ide.0,unit=0,drive=drive-ide0-0-0,id=ide0-0-0 \
 -full-screen \
--sdl \
+-display sdl \
 -vga cirrus

tests/qemuxml2argvdata/graphics-sdl.args

@@ -24,5 +24,5 @@ server,nowait \
 -usb \
 -drive file=/dev/HostVG/QEMUGuest1,format=raw,if=none,id=drive-ide0-0-0 \
 -device ide-drive,bus=ide.0,unit=0,drive=drive-ide0-0-0,id=ide0-0-0 \
--sdl \
+-display sdl \
 -vga std

tests/qemuxml2argvdata/video-virtio-gpu-sdl-gl.args

@@ -23,6 +23,6 @@ server,nowait \
 -drive file=/var/lib/libvirt/images/QEMUGuest1,format=qcow2,if=none,\
 id=drive-ide0-0-0,cache=none \
 -device ide-drive,bus=ide.0,unit=0,drive=drive-ide0-0-0,id=ide0-0-0 \
--sdl gl=on \
+-display sdl,gl=on \
 -device virtio-gpu-pci,id=video0,virgl=on,bus=pci.0,addr=0x2 \
 -device virtio-balloon-pci,id=balloon0,bus=pci.0,addr=0x3