Bug 510879: Remove requirement for suspended context in Disassembly View

Allow disassembled code to be displayed even while a running thread is
selected.  Switching from a suspended to a live thread does not clear
the view.  To initially get the disassembled code, a suspended context
is required.

Move the check for a frame context to the backend, allowing extenders to
provide custom symbol lookup by overriding
DisassemblyBackendDsf#evaluateAddressExpression.  Overriding this method
to provide custom lookup also allows fetching disassembled code from a
live thread.

Edit:  Make Disassembly message consistent so that prior to selecting a
suspended context the view shows 'No Debug Context'.  After selecting a
suspended context disassembly is shown for all nodes except launch.

Change-Id: I42c54b179b5dacc16f7a5e04a83ddb973ccc6dde
Signed-off-by: Stephen Flynn <stephen.flynn@dell.com>

debug/org.eclipse.cdt.debug.ui/src/org/eclipse/cdt/debug/internal/ui/disassembly/dsf/AbstractDisassemblyBackend.java

@@ -80,7 +80,7 @@ public abstract class AbstractDisassemblyBackend implements IDisassemblyBackend
 	
 	@Override
 	public boolean canDisassemble() {
-		return isSuspended();
+		return true;
 	}
 	
 	@Override

dsf/org.eclipse.cdt.dsf.ui/src/org/eclipse/cdt/dsf/debug/internal/ui/disassembly/DisassemblyBackendDsf.java

@@ -214,8 +214,13 @@ public class DisassemblyBackendDsf extends AbstractDisassemblyBackend implements
 		        		}
 					}
 		        }
-
+				// Ensures the view will display 'No Debug Context'
+				if (fTargetFrameContext != null) {
 					result.sessionId = fDsfSessionId = dsfSessionId;
+				} else {
+					fDsfSessionId = dsfSessionId;
+					result.sessionId = null;
+				}
 				if (fServicesTracker != null) {
 					fServicesTracker.dispose();
 				}
@@ -242,9 +247,16 @@ public class DisassemblyBackendDsf extends AbstractDisassemblyBackend implements
 			IFrameDMContext frame= (IFrameDMContext) dmContext;
 			IExecutionDMContext newExeDmc = DMContexts.getAncestorOfType(frame, IExecutionDMContext.class);
 			if (newExeDmc != null) {
-				IDisassemblyDMContext newDisDmc = DMContexts.getAncestorOfType(newExeDmc, IDisassemblyDMContext.class);
+				if (fTargetFrameContext != null) {
-				IDisassemblyDMContext oldDisDmc = DMContexts.getAncestorOfType(fTargetContext, IDisassemblyDMContext.class);
+					IDisassemblyDMContext newDisDmc = DMContexts.getAncestorOfType(newExeDmc,
+							IDisassemblyDMContext.class);
+					IDisassemblyDMContext oldDisDmc = DMContexts.getAncestorOfType(fTargetContext,
+							IDisassemblyDMContext.class);
 					result.contextChanged = !newDisDmc.equals(oldDisDmc);
+				} else {
+					// If switching from a thread node to a frame node
+					result.contextChanged = true;
+				}
 				fTargetContext= newExeDmc;
 				fTargetFrameContext= frame;
 				if (!result.contextChanged) {
@@ -255,10 +267,15 @@ public class DisassemblyBackendDsf extends AbstractDisassemblyBackend implements
 				fTargetFrameContext = null;
 				result.contextChanged = true;
 			}
+		} else if (dmContext instanceof IExecutionDMContext) {
+			// When switching to and between thread and application nodes.
+			result.sessionId = null;
+			result.contextChanged = false;
+			fTargetContext = (IExecutionDMContext) dmContext;
+			fTargetFrameContext = null;
 		} else if (dmContext.equals(fTargetContext) && canDisassemble()) {
 			result.contextChanged = false;
 			result.sessionId = fDsfSessionId;
-			
 		} else {			
 			fTargetContext = null;
 			fTargetFrameContext = null;
@@ -976,6 +993,9 @@ public class DisassemblyBackendDsf extends AbstractDisassemblyBackend implements
 	 */
 	@Override
 	public void gotoSymbol(final String symbol) {
+		if (!hasFrameContext()) {
+			return;
+		}
 		evaluateAddressExpression(symbol, false, new DataRequestMonitor<BigInteger>(getSession().getExecutor(), null) {			
 			@Override
 			protected void handleSuccess() {
@@ -997,6 +1017,10 @@ public class DisassemblyBackendDsf extends AbstractDisassemblyBackend implements
 	 */
 	@Override
 	public BigInteger evaluateAddressExpression(final String symbol, final boolean suppressError) {
+		// Without a suspended context, using the expressions service is pointless.
+		if (!hasFrameContext()) {
+			return null;
+		}
 		Query<BigInteger> query = new Query<BigInteger>() {
 			@Override
 			protected void execute(DataRequestMonitor<BigInteger> rm) {
@@ -1293,7 +1317,7 @@ public class DisassemblyBackendDsf extends AbstractDisassemblyBackend implements
 	 * @return
 	 */
 	protected boolean canDisassembleContext(IDMContext context) {
-		return context instanceof IFrameDMContext;
+		return DMContexts.getAncestorOfType(context, IExecutionDMContext.class) != null;
 	}
 	
 	/**

dsf/org.eclipse.cdt.dsf.ui/src/org/eclipse/cdt/dsf/debug/internal/ui/disassembly/DisassemblyPart.java

@@ -1448,7 +1448,7 @@ public abstract class DisassemblyPart extends WorkbenchPart implements IDisassem
 	 */
 	@Override
 	public final void gotoSymbol(final String symbol) {
-		if (!fActive || fBackend == null || !fBackend.hasFrameContext()) {
+		if (!fActive || fBackend == null) {
 			return;
 		}
 		fBackend.gotoSymbol(symbol);
@@ -1525,7 +1525,8 @@ public abstract class DisassemblyPart extends WorkbenchPart implements IDisassem
 		if (!fActive || fUpdatePending || fViewer == null || fDebugSessionId == null) {
 			return;
 		}
-		if (fBackend == null || !fBackend.hasDebugContext() || !fBackend.canDisassemble() || fFrameAddress == PC_UNKNOWN) {
+
+		if (fBackend == null || !fBackend.hasDebugContext() || !fBackend.canDisassemble()) {
 			return;
 		}
 		StyledText styledText = fViewer.getTextWidget();