From f20db296461976de41d0ca97696a5f49a77990ba Mon Sep 17 00:00:00 2001
From: Austin Adams <git@austinjadams.com>
Date: Wed, 3 Jun 2020 22:17:00 -0700
Subject: Pretend to get "stuck" on halts

---
 packages/novice-web/novice-web/components/GuiDebugger.tsx  |  6 +++++-
 packages/novice-web/novice-web/index.tsx                   |  2 +-
 .../novice-web/workers/debugger/debugger-worker.ts         | 14 ++++++++++++++
 packages/novice/novice/simulator/simulator.ts              |  4 ++++
 4 files changed, 24 insertions(+), 2 deletions(-)

diff --git a/packages/novice-web/novice-web/components/GuiDebugger.tsx b/packages/novice-web/novice-web/components/GuiDebugger.tsx
index baa62f2..f34f480 100644
--- a/packages/novice-web/novice-web/components/GuiDebugger.tsx
+++ b/packages/novice-web/novice-web/components/GuiDebugger.tsx
@@ -59,6 +59,10 @@ export class GuiDebugger extends React.Component<GuiDebuggerProps,
     }
 
     public render() {
+        // Be a little dishonest: to avoid confusing users, get 'stuck' on halts
+        const pc = this.state.state.halted ? this.state.state.pc - this.isa.spec.pc.increment
+                                           : this.state.state.pc;
+
         const registers = this.isa.spec.regs.map(reg => {
             let values;
 
@@ -80,7 +84,7 @@ export class GuiDebugger extends React.Component<GuiDebuggerProps,
         const rowHeight = 20;
         const cols = [20, 80, 80, 80, 200];
         const colVal: ((addr: number) => string)[] = [
-            addr => (this.state.state.pc === addr) ? '►' : '',
+            addr => (pc === addr) ? '►' : '',
             addr => this.fmtAddr(addr),
             addr => this.fmtWord(this.isa.stateLoad(this.state.state, addr)),
             addr => this.isa.stateLoad(this.state.state, addr).toString(10),
diff --git a/packages/novice-web/novice-web/index.tsx b/packages/novice-web/novice-web/index.tsx
index 213b51f..6de52cd 100644
--- a/packages/novice-web/novice-web/index.tsx
+++ b/packages/novice-web/novice-web/index.tsx
@@ -8,7 +8,7 @@ const ASSEMBLER_WORKER_BUNDLE_URL = 'dist/assemblerWorker.bundle.js';
 
 ReactDOM.render(
     <GuiDebugger isaName='lc3'
-                 initialAssemblyCode={'; write LC-3 assembly code here\n'}
+                 initialAssemblyCode={'.orig x3000\n; write LC-3 assembly code here\n\nhalt\n.end\n'}
                  debuggerWorkerBundleUrl={DEBUGGER_WORKER_BUNDLE_URL}
                  assemblerWorkerBundleUrl={ASSEMBLER_WORKER_BUNDLE_URL} />,
     document.getElementById('root'),
diff --git a/packages/novice-web/novice-web/workers/debugger/debugger-worker.ts b/packages/novice-web/novice-web/workers/debugger/debugger-worker.ts
index 90934cb..df12bdb 100644
--- a/packages/novice-web/novice-web/workers/debugger/debugger-worker.ts
+++ b/packages/novice-web/novice-web/workers/debugger/debugger-worker.ts
@@ -57,6 +57,20 @@ class DebuggerWorker extends BaseWorker<DebuggerFrontendMessage,
                     throw new Error('must reset before unstepping');
                 }
 
+                // Maintain the lie that the debugger "freezes" on a halt by
+                // double-unstepping on halts. Without this, after executing a
+                // halt, it seems like nothing happened.
+                //
+                // We do this here instead of the frontend in case the
+                // frontend batches up n unstep requests while sitting
+                // on a halt before getting any machine state updates
+                // from the debugger worker. In such a case, if we did
+                // this check in the frontend, we would send 2n unstep
+                // requests instead of correctly sending n + 1.
+                if (this.dbg.isHalted() && this.dbg.getLogLength() > 1) {
+                    this.dbg.unstep();
+                }
+
                 this.dbg.unstep();
                 break;
 
diff --git a/packages/novice/novice/simulator/simulator.ts b/packages/novice/novice/simulator/simulator.ts
index f0620bf..3e21a80 100644
--- a/packages/novice/novice/simulator/simulator.ts
+++ b/packages/novice/novice/simulator/simulator.ts
@@ -29,6 +29,10 @@ class Simulator implements Memory {
 
     public getNumExec() { return this.numExec; }
 
+    public getLogLength(): number {
+        return this.log.length;
+    }
+
     public loadSections(sections: MachineCodeSection[]): void {
         const updates: MachineStateUpdate[] = [];
 
-- 
cgit v1.0-2-geb64