Add OS-aware install wizard for g++/OpenGL deps, with confirm-before-install and proper cancel handling

Author: pepc84

src/java/CppBuild.java

@@ -238,8 +238,10 @@ private void checkGppAvailable(RunnerListener listener) throws Exception {
       try { if (Runtime.getRuntime().exec(new String[]{"g++","--version"}).waitFor()==0) return; }
       catch (Exception ignored) {}
 
-      // Try the guided installer first. If it succeeds, we're done; if the
-      // user cancels or it fails, fall through to the existing dialog below.
+      // Try the guided installer first. If it succeeds, we're done. If the
+      // user cancels, InstallWizard throws CancelledByUser, which stops
+      // the build entirely instead of falling through. Only a genuine
+      // wizard failure (not a cancel) falls through to the dialog below.
       if (InstallWizard.run(listener)) return;
 
       Object[] opts = { "Install Automatically", "Download MSYS2", "Cancel" };
@@ -272,8 +274,8 @@ else if (ch == 1) {
       catch (Exception ignored) {}
       if (isMac) {
         // Try the guided installer first (Xcode Command Line Tools, then
-        // GLFW/GLEW via Homebrew if present). Falls through to the
-        // existing dialog below if cancelled or unsuccessful.
+        // GLFW/GLEW via Homebrew if present). A cancel throws and stops
+        // the build; only a genuine failure falls through to the dialog.
         if (InstallWizard.run(listener)) return;
 
         showGppDialog(
@@ -283,8 +285,8 @@ else if (ch == 1) {
           + "Click Download Homebrew if not installed.</html>",
           "Download Homebrew", "https://brew.sh", listener);
       } else {
-        // Try the guided installer first. Falls through to the existing
-        // package-manager dialog below if cancelled or unsuccessful.
+        // Try the guided installer first. A cancel throws and stops the
+        // build; only a genuine failure falls through to the dialog below.
         if (InstallWizard.run(listener)) return;
 
         // Detect package manager and offer auto-install
@@ -441,7 +443,7 @@ private boolean commandExists(String cmd) {
     } catch (Exception e) { return false; }
   }
 
-  private void checkNativeLibs(RunnerListener listener, File binary) {
+  private void checkNativeLibs(RunnerListener listener, File binary) throws Exception {
     String os   = System.getProperty("os.name").toLowerCase();
     boolean win = os.contains("win");
     boolean mac = os.contains("mac");
@@ -466,7 +468,7 @@ private boolean windowsLibsNowPresent(java.util.List<String> searchDirs, String[
     return true;
   }
 
-  private void checkWindowsDLLs(RunnerListener listener, File binary) {
+  private void checkWindowsDLLs(RunnerListener listener, File binary) throws Exception {
     String[] required = { "glfw3.dll", "glew32.dll" };
     java.util.List<String> searchDirs = new java.util.ArrayList<>();
     searchDirs.add(binary.getParent());
@@ -557,7 +559,7 @@ private void checkWindowsDLLs(RunnerListener listener, File binary) {
   }
 
   // ── macOS ──────────────────────────────────────────────────────────────────
-  private void checkMacLibs(RunnerListener listener) {
+  private void checkMacLibs(RunnerListener listener) throws Exception {
     // Check for glfw and glew via pkg-config or known Homebrew paths
     boolean glfwOk = new File("/opt/homebrew/lib/libglfw.dylib").exists()
                   || new File("/usr/local/lib/libglfw.dylib").exists()
@@ -626,7 +628,7 @@ private void checkMacLibs(RunnerListener listener) {
   }
 
   // ── Linux ──────────────────────────────────────────────────────────────────
-  private void checkLinuxLibs(RunnerListener listener) {
+  private void checkLinuxLibs(RunnerListener listener) throws Exception {
     boolean glfwOk = new File("/usr/lib/libglfw.so").exists()
                   || new File("/usr/lib/x86_64-linux-gnu/libglfw.so").exists()
                   || new File("/usr/lib/x86_64-linux-gnu/libglfw.so.3").exists()

src/java/CppEditor.java

@@ -395,6 +395,9 @@ public void handleRun(boolean present, Runnable stopCb, Runnable startCb) {
           statusError("Build failed — see console for errors.");
           deactivateRun();
         }
+      } catch (InstallWizard.CancelledByUser e) {
+        statusNotice("Cancelled.");
+        deactivateRun();
       } catch (Exception e) {
         statusError(e.getMessage());
         deactivateRun();

src/java/InstallWizard.java

@@ -24,6 +24,16 @@
  */
 public class InstallWizard {
 
+  /**
+   * Thrown when the user explicitly cancels the wizard (at the initial
+   * missing-dependencies prompt, or mid-install). Callers should treat
+   * this as "stop entirely" rather than falling back to other dialogs —
+   * the user made a deliberate choice not to proceed.
+   */
+  public static class CancelledByUser extends Exception {
+    public CancelledByUser() { super("Installation cancelled by user."); }
+  }
+
   /**
    * Checks what's missing and, if anything is, shows a plain error dialog
    * first ("Missing: g++, glfw" + Install/Cancel). Only if the user clicks
@@ -34,7 +44,7 @@ public class InstallWizard {
    *         this returns; false if the user cancelled or installation
    *         could not be completed.
    */
-  public static boolean run(RunnerListener listener) {
+  public static boolean run(RunnerListener listener) throws CancelledByUser {
     String os = System.getProperty("os.name").toLowerCase();
     InstallWizard w = new InstallWizard();
 
@@ -52,6 +62,8 @@ public static boolean run(RunnerListener listener) {
     } else {
       // Unrecognized OS — we don't know how to install anything here, so
       // just tell the user exactly what's needed and let them sort it out.
+      // This isn't a cancellation, so it returns false rather than
+      // throwing — CppBuild's caller can still decide what to do next.
       java.util.List<String> generic = new java.util.ArrayList<>();
       generic.add("g++ (a C++17-capable compiler)");
       generic.add("glfw");
@@ -91,16 +103,22 @@ public static boolean run(RunnerListener listener) {
       }
     }
 
-    if (!proceed[0]) return false;
+    if (!proceed[0]) throw new CancelledByUser();
 
     // User confirmed — now open the real progress wizard and install.
+    // A cancel from inside the wizard itself also surfaces as
+    // CancelledByUser (checked via w.cancelled right after each call),
+    // distinguishing "user backed out" from "install genuinely failed".
+    boolean result;
     if (isWin) {
-      return w.runWindows(missing);
+      result = w.runWindows(missing);
     } else if (isMac) {
-      return w.runMac(missing);
+      result = w.runMac(missing);
     } else {
-      return w.runLinux(missing);
+      result = w.runLinux(missing);
     }
+    if (!result && w.cancelled.get()) throw new CancelledByUser();
+    return result;
   }
 
   // ── Shared dialog plumbing ────────────────────────────────────────────