9 files changed, 170 insertions, 25 deletions

diff --git a/src/app.c b/src/app.c
index 2f1e435b..29d8cac4 100644
--- a/src/app.c
+++ b/src/app.c
@@ -406,7 +406,10 @@ static iBool loadState_App_(iApp *d) {
             readData_File(f, 4, magic);
             if (!memcmp(magic, magicTabDocument_App_, 4)) {
                 const int8_t flags = read8_File(f);
-                const int rootIndex = flags & rootIndex1_DocumentStateFlag ? 1 : 0;
+                int rootIndex = flags & rootIndex1_DocumentStateFlag ? 1 : 0;
+                if (rootIndex > numRoots_Window(d->window) - 1) {
+                    rootIndex = 0;
+                }
                 setCurrent_Root(d->window->roots[rootIndex]);
                 if (isFirstTab[rootIndex]) {
                     isFirstTab[rootIndex] = iFalse;
@@ -1148,9 +1151,12 @@ static int run_App_(iApp *d) {
     while (d->isRunning) {
         dispatchCommands_Periodic(&d->periodic);
         processEvents_App(waitForNewEvents_AppEventMode);
-        setCurrent_Root(NULL);
         runTickers_App_(d);
         refresh_App();
+        /* Change the widget tree while we are not iterating through it. */
+        if (d->window->splitMode != d->window->pendingSplitMode) {
+            setSplitMode_Window(d->window, d->window->pendingSplitMode);
+        }
         recycle_Garbage();
     }
     SDL_DelEventWatch(resizeWatcher_, d);
@@ -1654,6 +1660,15 @@ iBool handleCommand_App(const char *cmd) {
         d->prefs.langTo   = argLabel_Command(cmd, "to");
         return iTrue;
     }
+    else if (equal_Command(cmd, "ui.frames")) {
+        d->window->pendingSplitMode =
+            (argLabel_Command(cmd, "axis") ? vertical_WindowSplit : 0) | (arg_Command(cmd) << 1);
+        return iTrue;
+    }
+//    else if (equal_Command(cmd, "window.updatelayout")) {
+//        resize_Window(d->window, -1, -1);
+//        return iTrue;
+//    }
     else if (equal_Command(cmd, "window.retain")) {
         d->prefs.retainWindowSize = arg_Command(cmd);
         return iTrue;
@@ -2009,15 +2024,22 @@ iBool handleCommand_App(const char *cmd) {
             arrange_Widget(tabs);
             return iTrue;
         }
-        if (tabCount_Widget(tabs) > 1) {
+        const iBool isSplit = numRoots_Window(get_Window()) > 1;
+        if (tabCount_Widget(tabs) > 1 || isSplit) {
             iWidget *closed = removeTabPage_Widget(tabs, index);
             destroy_Widget(closed); /* released later */
             if (index == tabCount_Widget(tabs)) {
                 index--;
             }
-            arrange_Widget(tabs);
-            if (wasCurrent) {
-                postCommandf_App("tabs.switch page:%p", tabPage_Widget(tabs, index));
+            if (tabCount_Widget(tabs) == 0) {
+                iAssert(isSplit);
+                postCommand_App("ui.frames arg:0");
+            }
+            else {
+                arrange_Widget(tabs);
+                if (wasCurrent) {
+                    postCommandf_App("tabs.switch page:%p", tabPage_Widget(tabs, index));
+                }
             }
         }
         else {
@@ -2113,7 +2135,7 @@ iBool handleCommand_App(const char *cmd) {
         const iPtrArray *homepages =
             list_Bookmarks(d->bookmarks, NULL, filterTagsRegExp_Bookmarks, pattern);
         if (isEmpty_PtrArray(homepages)) {
-            postCommand_App("open url:about:lagrange");
+            postCommand_Root(get_Root(), "open url:about:lagrange");
         }
         else {
             iStringSet *urls = iClob(new_StringSet());
@@ -2125,13 +2147,13 @@ iBool handleCommand_App(const char *cmd) {
                 }
             }
             if (!isEmpty_StringSet(urls)) {
-                postCommandf_App(
+                postCommandf_Root(get_Root(),
                     "open url:%s",
                     cstr_String(constAt_StringSet(urls, iRandoms(0, size_StringSet(urls)))));
             }
         }
         if (argLabel_Command(cmd, "focus")) {
-            postCommand_App("navigate.focus");
+            postCommand_Root(get_Root(), "navigate.focus");
         }
         return iTrue;
     }
@@ -2335,6 +2357,7 @@ iObjectList *listDocuments_App(const iRoot *rootOrNull) {
     iObjectList *docs = new_ObjectList();
     iForIndices(i, win->roots) {
         iRoot *root = win->roots[i];
+        if (!root) continue;
         if (!rootOrNull || root == rootOrNull) {
             const iWidget *tabs = findChild_Widget(root->widget, "doctabs");
             iForEach(ObjectList, i, children_Widget(findChild_Widget(tabs, "tabs.pages"))) {
diff --git a/src/ui/documentwidget.c b/src/ui/documentwidget.c
index 21c0aa23..410b793e 100644
--- a/src/ui/documentwidget.c
+++ b/src/ui/documentwidget.c
@@ -3969,6 +3969,11 @@ static iBool render_DocumentWidget_(const iDocumentWidget *d, iDrawContext *ctx,
 }
 
 static void prerender_DocumentWidget_(iAny *context) {
+    if (current_Root() == NULL) {
+        /* The widget has probably been removed from the widget tree, pending destruction.
+           Tickers are not cancelled until the widget is actually destroyed. */
+        return;
+    }
     const iDocumentWidget *d = context;
     iDrawContext ctx = {
         .widget          = d,
diff --git a/src/ui/root.c b/src/ui/root.c
index 247faf38..2eca982c 100644
--- a/src/ui/root.c
+++ b/src/ui/root.c
@@ -304,6 +304,12 @@ static iBool handleRootCommands_(iWidget *root, const char *cmd) {
         }
         return iTrue;
     }
+    else if (equal_Command(cmd, "splitmenu.open")) {
+        iWidget *menu = findWidget_Root("splitmenu");
+        openMenu_Widget(menu, zero_I2());
+        setPos_Widget(menu, sub_I2(divi_I2(size_Root(get_Root()), 2), divi_I2(menu->rect.size, 2)));
+        return iTrue;
+    }
     else if (equal_Command(cmd, "contextclick")) {
         iBool showBarMenu = iFalse;
         if (equal_Rangecc(range_Command(cmd, "id"), "buttons")) {
@@ -879,7 +885,7 @@ void updateMetrics_Root(iRoot *d) {
 }
 
 void createUserInterface_Root(iRoot *d) {
-    iWidget *root = d->widget = new_Widget();
+    iWidget *root = d->widget = new_Widget();    
     iAssert(root->root == d);
     setId_Widget(root, "root");
     /* Children of root cover the entire window. */
@@ -1231,9 +1237,22 @@ void createUserInterface_Root(iRoot *d) {
                                                 { clipboard_Icon " ${menu.paste}", 0, 0, "input.paste" },
                                                 },
                                             4);
+        iWidget *splitMenu = makeMenu_Widget(root, (iMenuItem[]){
+            { "Single Frame", '1', 0, "ui.frames arg:0" },
+            { "---", 0, 0, NULL },
+            { "Horizontal", '2', 0, "ui.frames arg:3 axis:0" },
+            { "Horizontal 1:2", SDLK_d, 0, "ui.frames arg:1 axis:0" },
+            { "Horizontal 2:1", SDLK_e, 0, "ui.frames arg:2 axis:0" },
+            { "---", 0, 0, NULL },
+            { "Vertical", '3', 0, "ui.frames arg:3 axis:1" },
+            { "Vertical 1:2", SDLK_f, 0, "ui.frames arg:1 axis:1" },
+            { "Vertical 2:1", SDLK_r, 0, "ui.frames arg:2 axis:1" },
+        }, 9);
+        setFlags_Widget(splitMenu, disabledWhenHidden_WidgetFlag, iTrue); /* enabled when open */
         setId_Widget(tabsMenu, "doctabs.menu");
         setId_Widget(barMenu, "barmenu");
         setId_Widget(clipMenu, "clipmenu");
+        setId_Widget(splitMenu, "splitmenu");
     }
     /* Global keyboard shortcuts. */ {
         addAction_Widget(root, 'l', KMOD_PRIMARY, "navigate.focus");
@@ -1248,6 +1267,7 @@ void createUserInterface_Root(iRoot *d) {
         addAction_Widget(root, '3', rightSidebar_KeyModifier, "sidebar2.mode arg:2 toggle:1");
         addAction_Widget(root, '4', rightSidebar_KeyModifier, "sidebar2.mode arg:3 toggle:1");
         addAction_Widget(root, '5', rightSidebar_KeyModifier, "sidebar2.mode arg:4 toggle:1");
+        addAction_Widget(root, SDLK_j, KMOD_PRIMARY, "splitmenu.open");
     }
     updateMetrics_Root(d);
 }
diff --git a/src/ui/util.c b/src/ui/util.c
index a1d76709..fd8740b4 100644
--- a/src/ui/util.c
+++ b/src/ui/util.c
@@ -984,6 +984,14 @@ void prependTabPage_Widget(iWidget *tabs, iWidget *page, const char *label, int
     addTabPage_Widget_(tabs, front_WidgetAddPos, page, label, key, kmods);
 }
 
+void moveTabButtonToEnd_Widget(iWidget *tabButton) {
+    iWidget *buttons = tabButton->parent;
+    iWidget *tabs    = buttons->parent;
+    removeChild_Widget(buttons, tabButton);
+    addChild_Widget(buttons, iClob(tabButton));
+    arrange_Widget(tabs);
+}
+
 iWidget *tabPage_Widget(iWidget *tabs, size_t index) {
     iWidget *pages = findChild_Widget(tabs, "tabs.pages");
     return child_Widget(pages, index);
diff --git a/src/ui/util.h b/src/ui/util.h
index 8dd16a7f..cbedefaa 100644
--- a/src/ui/util.h
+++ b/src/ui/util.h
@@ -246,6 +246,7 @@ void            setTabPageLabel_Widget  (iWidget *tabs, const iAnyObject *page,
 iWidget *       tabPage_Widget          (iWidget *tabs, size_t index);
 iLabelWidget *  tabPageButton_Widget    (iWidget *tabs, const iAnyObject *page);
 iBool           isTabButton_Widget      (const iWidget *);
+void            moveTabButtonToEnd_Widget(iWidget *tabButton);
 size_t          tabPageIndex_Widget     (const iWidget *tabs, const iAnyObject *page);
 const iWidget * currentTabPage_Widget   (const iWidget *tabs);
 size_t          tabCount_Widget         (const iWidget *tabs);
diff --git a/src/ui/widget.c b/src/ui/widget.c
index 590dbe70..e4d92b35 100644
--- a/src/ui/widget.c
+++ b/src/ui/widget.c
@@ -225,6 +225,13 @@ void setCommandHandler_Widget(iWidget *d, iBool (*handler)(iWidget *, const char
     d->commandHandler = handler;
 }
 
+void setRoot_Widget(iWidget *d, iRoot *root) {
+    d->root = root;
+    iForEach(ObjectList, i, d->children) {
+        setRoot_Widget(i.object, root);
+    }
+}
+
 static int numExpandingChildren_Widget_(const iWidget *d) {
     int count = 0;
     iConstForEach(ObjectList, i, d->children) {
@@ -749,7 +756,8 @@ iLocalDef iBool isMouseEvent_(const SDL_Event *ev) {
 static iBool filterEvent_Widget_(const iWidget *d, const SDL_Event *ev) {
     const iBool isKey   = isKeyboardEvent_(ev);
     const iBool isMouse = isMouseEvent_(ev);
-    if (d->flags & disabled_WidgetFlag) {
+    if ((d->flags & disabled_WidgetFlag) || (d->flags & hidden_WidgetFlag &&
+                                             d->flags & disabledWhenHidden_WidgetFlag)) {
         if (isKey || isMouse) return iFalse;
     }
     if (d->flags & hidden_WidgetFlag) {
diff --git a/src/ui/widget.h b/src/ui/widget.h
index 2ef035b6..c3c9609e 100644
--- a/src/ui/widget.h
+++ b/src/ui/widget.h
@@ -116,6 +116,7 @@ enum iWidgetFlag {
 #define parentCannotResizeHeight_WidgetFlag iBit64(58)
 #define ignoreForParentWidth_WidgetFlag     iBit64(59)
 #define noFadeBackground_WidgetFlag         iBit64(60)
+#define disabledWhenHidden_WidgetFlag       iBit64(61)
 
 enum iWidgetAddPos {
     back_WidgetAddPos,
@@ -247,6 +248,7 @@ void    showCollapsed_Widget        (iWidget *, iBool show); /* takes care of re
 void    setBackgroundColor_Widget   (iWidget *, int bgColor);
 void    setFrameColor_Widget        (iWidget *, int frameColor);
 void    setCommandHandler_Widget    (iWidget *, iBool (*handler)(iWidget *, const char *));
+void    setRoot_Widget              (iWidget *, iRoot *root); /* updates the entire tree */
 iAny *  addChild_Widget             (iWidget *, iAnyObject *child); /* holds a ref */
 iAny *  addChildPos_Widget          (iWidget *, iAnyObject *child, enum iWidgetAddPos addPos);
 iAny *  addChildPosFlags_Widget     (iWidget *, iAnyObject *child, enum iWidgetAddPos addPos, int64_t childFlags);
diff --git a/src/ui/window.c b/src/ui/window.c
index 54f05a20..da1db514 100644
--- a/src/ui/window.c
+++ b/src/ui/window.c
@@ -161,7 +161,7 @@ static void removeMacMenus_(void) {
 }
 #endif
 
-static int numRoots_Window(const iWindow *d) {
+int numRoots_Window(const iWindow *d) {
     int num = 0;
     iForIndices(i, d->roots) {
         if (d->roots[i]) num++;
@@ -173,27 +173,38 @@ static void setupUserInterface_Window(iWindow *d) {
 #if defined (iPlatformAppleDesktop)
     insertMacMenus_();
 #endif
-    iForIndices(i, d->roots) {
-        d->roots[i] = new_Root();
-        setCurrent_Root(d->roots[i]);
-        createUserInterface_Root(d->roots[i]);
-        setCurrent_Root(NULL);
-    }
+    /* One root is created by default. */
+    d->roots[0] = new_Root();
+    setCurrent_Root(d->roots[0]);
+    createUserInterface_Root(d->roots[0]);
+    setCurrent_Root(NULL);
     /* One of the roots always has keyboard input focus. */
     d->keyRoot = d->roots[0];
 }
 
 static void windowSizeChanged_Window_(iWindow *d) {
     const int numRoots = numRoots_Window(d);
-    /* Horizontal split frame. */
     const iInt2 rootSize = d->size;
+    const int weights[2] = {
+        d->roots[0] ? (d->splitMode & twoToOne_WindowSplit ? 2 : 1) : 0,
+        d->roots[1] ? (d->splitMode & oneToTwo_WindowSplit ? 2 : 1) : 0,
+    };
+    const int totalWeight = weights[0] + weights[1];
+    int w = 0;
     iForIndices(i, d->roots) {
         iRoot *root = d->roots[i];
         if (root) {
             iRect *rect = &root->widget->rect;
             /* Horizontal split frame. */
-            rect->pos  = init_I2(rootSize.x * i / numRoots, 0);
-            rect->size = init_I2(rootSize.x * (i + 1) / numRoots - rect->pos.x, rootSize.y);
+            if (d->splitMode & vertical_WindowSplit) {
+                rect->pos  = init_I2(0, rootSize.y * w / totalWeight);
+                rect->size = init_I2(rootSize.x, rootSize.y * (w + weights[i]) / totalWeight - rect->pos.y);
+            }
+            else {
+                rect->pos  = init_I2(rootSize.x * w / totalWeight, 0);
+                rect->size = init_I2(rootSize.x * (w + weights[i]) / totalWeight - rect->pos.x, rootSize.y);
+            }
+            w += weights[i];
             root->widget->minSize = rect->size;
             updatePadding_Root(root);
             arrange_Widget(root->widget);
@@ -378,6 +389,7 @@ void init_Window(iWindow *d, iRect rect) {
     d->win = NULL;
     d->size = zero_I2(); /* will be updated below */
     iZap(d->roots);
+    d->splitMode = d->pendingSplitMode = 0;
     d->hover = NULL;
     d->mouseGrab = NULL;
     d->focus = NULL;
@@ -1004,7 +1016,8 @@ void draw_Window(iWindow *d) {
                         &(SDL_Rect){ left_Rect(rect) + gap_UI * 1.25f, mid.y - size / 2, size, size });
                 }
 #endif
-                /* Root separator and keyboard focus indicator. */ {
+                /* Root separator and keyboard focus indicator. */
+                if (numRoots_Window(d) > 1){
                     iPaint p;
                     init_Paint(&p);
                     const iRect bounds = bounds_Widget(root->widget);
@@ -1017,7 +1030,7 @@ void draw_Window(iWindow *d) {
                     if (root == d->keyRoot) {
                         fillRect_Paint(&p, (iRect){
                             topLeft_Rect(bounds),
-                            init_I2(width_Rect(bounds), gap_UI / 2)                            
+                            init_I2(width_Rect(bounds), gap_UI / 2)
                         }, uiBackgroundSelected_ColorId);
                     }
                 }
@@ -1037,8 +1050,13 @@ void draw_Window(iWindow *d) {
 }
 
 void resize_Window(iWindow *d, int w, int h) {
-    SDL_SetWindowSize(d->win, w, h);
-    updateSize_Window_(d, iFalse);
+    if (w > 0 && h > 0) {
+        SDL_SetWindowSize(d->win, w, h);
+        updateSize_Window_(d, iFalse);
+    }
+    else {
+        updateSize_Window_(d, iTrue); /* notify always */
+    }
 }
 
 void setTitle_Window(iWindow *d, const iString *title) {
@@ -1126,6 +1144,51 @@ void setKeyboardHeight_Window(iWindow *d, int height) {
     }
 }
 
+void setSplitMode_Window(iWindow *d, int splitMode) {
+    iAssert(current_Root() == NULL);
+    if (d->splitMode != splitMode) {
+        int oldCount = numRoots_Window(d);
+        setFreezeDraw_Window(d, iTrue);
+        if (oldCount == 2 && splitMode == 0) {
+            /* Keep references to the tabs of the second root. */
+            iObjectList *tabs = listDocuments_App(d->roots[1]);
+            iForEach(ObjectList, i, tabs) {
+                setRoot_Widget(i.object, d->roots[0]);
+            }
+            delete_Root(d->roots[1]);
+            d->roots[1] = NULL;
+            d->keyRoot = d->roots[0];
+            /* Move the deleted root's tabs to the first root. */
+            setCurrent_Root(d->roots[0]);
+            iWidget *docTabs = findWidget_Root("doctabs");
+            iForEach(ObjectList, j, tabs) {
+                appendTabPage_Widget(docTabs, j.object, "", 0, 0);
+            }
+            /* The last child is the [+] button for adding a tab. */
+            moveTabButtonToEnd_Widget(findChild_Widget(docTabs, "newtab"));
+            iRelease(tabs);
+        }
+        else if ((splitMode & mask_WindowSplit) && oldCount == 1) {
+            /* Add a second root. */
+            iAssert(d->roots[1] == NULL);
+            d->roots[1] = new_Root();
+            setCurrent_Root(d->roots[1]);
+            createUserInterface_Root(d->roots[1]);
+            /* If the old root has multiple tabs, move the current one to the new split. */
+            
+            postCommand_Root(d->roots[1], "navigate.home");
+            setCurrent_Root(NULL);
+        }
+        d->splitMode = splitMode;
+//        windowSizeChanged_Window_(d);
+        updateSize_Window_(d, iTrue);
+//        postCommand_App("window.resized");
+  //      postCommand_App("metrics.resized");
+//        postCommand_App("window.updatelayout");
+        postCommand_App("window.unfreeze");
+    }
+}
+
 void setSnap_Window(iWindow *d, int snapMode) {
     if (!prefs_App()->customFrame) {
         if (snapMode == maximized_WindowSnap) {
diff --git a/src/ui/window.h b/src/ui/window.h
index b2b22e90..ad577ce4 100644
--- a/src/ui/window.h
+++ b/src/ui/window.h
@@ -56,6 +56,17 @@ struct Impl_WindowPlacement {
     int   lastHit;
 };
 
+enum iWindowSplit {
+    vertical_WindowSplit = iBit(1),
+    oneToTwo_WindowSplit = iBit(2),
+    twoToOne_WindowSplit = iBit(3),
+    equal_WindowSplit    = oneToTwo_WindowSplit | twoToOne_WindowSplit,
+    /* meta */
+    mode_WindowSplit     = vertical_WindowSplit | equal_WindowSplit,
+    mask_WindowSplit     = equal_WindowSplit,
+    merge_WindowSplit    = iBit(10),
+};
+
 struct Impl_Window {
     SDL_Window *  win;
     iWindowPlacement place;
@@ -67,6 +78,8 @@ struct Impl_Window {
     uint32_t      focusGainedAt;
     SDL_Renderer *render;
     iInt2         size;
+    int           splitMode;
+    int           pendingSplitMode;
     iRoot *       roots[2];     /* root widget and UI state; second one is for split mode */
     iRoot *       keyRoot;      /* root that has the current keyboard input focus */
     iWidget *     hover;
@@ -98,6 +111,7 @@ iBool       setKeyRoot_Window       (iWindow *, iRoot *root);
 void        setCursor_Window        (iWindow *, int cursor);
 void        setSnap_Window          (iWindow *, int snapMode);
 void        setKeyboardHeight_Window(iWindow *, int height);
+void        setSplitMode_Window     (iWindow *, int splitMode);
 void        showToolbars_Window     (iWindow *, iBool show);
 iBool       postContextClick_Window (iWindow *, const SDL_MouseButtonEvent *);
 
@@ -112,6 +126,7 @@ uint32_t    frameTime_Window        (const iWindow *);
 SDL_Renderer *renderer_Window       (const iWindow *);
 int         snap_Window             (const iWindow *);
 iBool       isFullscreen_Window     (const iWindow *);
+int         numRoots_Window         (const iWindow *);
 iRoot *     findRoot_Window         (const iWindow *, const iWidget *widget);
 iRoot *     otherRoot_Window        (const iWindow *, iRoot *root);