PatchBay: complain when there are no MIDI devices

The empty window that would show when no MIDI devices are found would
confuse Haiku users. This was not a problem on the BeBox or older PCs
where a sound card with MPU401 port was standard, so there would always
be something to show.

Fixes #9977.

src/apps/patchbay/Jamfile

@@ -11,8 +11,13 @@ SimpleTest PatchBay
 	EndpointInfo.cpp
 	MidiEventMeter.cpp
 	:
-	midi midi2 be libicon.a [ TargetLibstdc++ ]
+	midi midi2 be libicon.a localestub [ TargetLibstdc++ ]
 	:
 	PatchBay.rdef
 ;
 
+DoCatalogs PatchBay :
+	x-vnd.Haiku.PatchBay
+	:
+	PatchView.cpp
+;

src/apps/patchbay/PatchView.cpp

@@ -15,6 +15,7 @@
 
 #include <Application.h>
 #include <Bitmap.h>
+#include <Catalog.h>
 #include <Debug.h>
 #include <IconUtils.h>
 #include <InterfaceDefs.h>
@@ -28,6 +29,9 @@
 #include "UnknownDeviceIcons.h"
 
 
+#define B_TRANSLATION_CONTEXT "Patch Bay"
+
+
 PatchView::PatchView(BRect rect)
 	:
 	BView(rect, "PatchView", B_FOLLOW_ALL, B_WILL_DRAW),
@@ -149,14 +153,31 @@ PatchView::Draw(BRect /* updateRect */)
 			const BBitmap* bitmap = (i->Icon()) ? i->Icon() : fUnknownDeviceIcon;
 			DrawBitmapAsync(bitmap, RowIconFrameAt(index++).LeftTop());
 	}
-			
+
 	// draw consumer icons
-	index = 0;
+	int32 index2 = 0;
 	for (list<EndpointInfo>::const_iterator i = fConsumers.begin();
 		i != fConsumers.end(); i++) {
 			const BBitmap* bitmap = (i->Icon()) ? i->Icon() : fUnknownDeviceIcon;
-			DrawBitmapAsync(bitmap, ColumnIconFrameAt(index++).LeftTop());
+			DrawBitmapAsync(bitmap, ColumnIconFrameAt(index2++).LeftTop());
 	}
+
+	if (index == 0 && index2 == 0) {
+		const char* message = B_TRANSLATE("No MIDI devices found!");
+		float width = StringWidth(message);
+		BRect rect = Bounds();
+
+		rect.top = rect.top + rect.bottom / 2;
+		rect.left = rect.left + rect.right / 2;
+		rect.left -= width / 2;
+
+		DrawString(message, rect.LeftTop());
+
+		// Since the message is centered, we need to redraw the whole view in
+		// this case.
+		SetFlags(Flags() | B_FULL_UPDATE_ON_RESIZE);
+	} else
+		SetFlags(Flags() & ~B_FULL_UPDATE_ON_RESIZE);
 }