Implement getcellpixels() for MacVim

Don't use `gui.char_width` / `char_height` unlike the other GVim
implementations. Those are used for deriving screen pixel sizes and
MacVim has been hard-coding them to 1 for simplicity since the actual
GUI functionality is handled out of the Vim process anyway. Changing
those values would require some refactoring. Instead, just use a new
variable to store them.

Note that there is a delay with this method, as we only update Vim's
knowledge of cell size after MacVim has received the font change
message. This means if a user wants to immediately query getcellpixels()
in vimrc or after changing guifont this will not work. This is a
deliberate design choice to avoid having to add synchronous state query
APIs to MacVim, but it's possible to change it in the future. The
handling of this message did get placed in `processInput:` which means
it will be picked up whenever we sleep or process messages in Vim,
instead of only when waiting for keys (where most of other MacVim
messages are handled in `processInputQueue`).

Related: vim/vim#16004

Author: ychin

src/MacVim/MMBackend.h

@@ -57,6 +57,8 @@
 #endif
 }
 
+@property (nonatomic, readonly) NSSize cellSize;
+
 + (MMBackend *)sharedInstance;
 
 - (void)setBackgroundColor:(int)color;

src/MacVim/MMBackend.m

@@ -1328,6 +1328,9 @@ - (oneway void)processInput:(int)msgid data:(in bycopy NSData *)data
         // modified files when we get here.
         isTerminating = YES;
         getout(0);
+    } else if (UpdateCellSizeMsgID == msgid) {
+        // Immediately handle simple state updates to they can be reflected in Vim.
+        [self handleCellSize:data];
     } else {
         // First remove previous instances of this message from the input
         // queue, else the input queue may fill up as a result of Vim not being
@@ -2705,6 +2708,18 @@ - (void)handleSetFont:(NSData *)data
     CONVERT_FROM_UTF8_FREE(s);
 }
 
+- (void)handleCellSize:(NSData *)data
+{
+    if (!data) return;
+
+    const void *bytes = [data bytes];
+
+    // Don't use gui.char_width/height because for simplicity we set those to
+    // 1. We store the cell size separately (it's only used for
+    // getcellpixels()).
+    memcpy(&_cellSize, bytes, sizeof(NSSize));
+}
+
 - (void)handleDropFiles:(NSData *)data
 {
     // TODO: Get rid of this method; instead use Vim script directly.  At the

src/MacVim/MMVimController.m

@@ -1012,6 +1012,14 @@ - (void)handleMessage:(int)msgid data:(NSData *)data
             }
 
             [windowController setFont:font];
+
+            // Notify Vim of updated cell size for getcellpixels(). Note that
+            // this is asynchronous, which means getcellpixels() will not be
+            // immediately reflected after setting guifont.
+            NSSize cellsize = windowController.vimView.textView.cellSize;
+            [self sendMessage:UpdateCellSizeMsgID
+                         data:[NSData dataWithBytes:&cellsize length:sizeof(cellsize)]];
+
             [name release];
         }
         break;

src/MacVim/MacVim.h

@@ -300,6 +300,7 @@ extern const char * const MMVimMsgIDStrings[];
     MSG(ScrollbarEventMsgID) \
     MSG(SetFontMsgID) \
     MSG(SetWideFontMsgID) \
+    MSG(UpdateCellSizeMsgID) \
     MSG(VimShouldCloseMsgID) \
     MSG(SetDefaultColorsMsgID) \
     MSG(SetTablineColorsMsgID) \

src/MacVim/gui_macvim.m

@@ -247,6 +247,9 @@
     // correspondence (assuming all characters have the same dimensions).
     gui.scrollbar_width = gui.scrollbar_height = 0;
 
+    // For simplicity we just set char width/height to 1 as the GUI is
+    // decoupled from Vim anyway so Vim doesn't need to know the accurate
+    // pixel sizes.
     gui.char_height = 1;
     gui.char_width = 1;
     gui.char_ascent = 0;
@@ -1664,6 +1667,14 @@
     return OK;
 }
 
+    void
+gui_mch_calc_cell_size(struct cellsize *cs_out)
+{
+    NSSize cellsize = [MMBackend sharedInstance].cellSize;
+    cs_out->cs_xpixel = round(cellsize.width);
+    cs_out->cs_ypixel = round(cellsize.height);
+}
+
 
     void
 gui_mch_beep(void)

src/evalfunc.c

@@ -5425,8 +5425,15 @@ f_getcellpixels(typval_T *argvars UNUSED, typval_T *rettv)
     if (gui.in_use)
     {
         // success pixel size and no gui.
+#ifdef FEAT_GUI_MACVIM
+        struct cellsize cs;
+        gui_mch_calc_cell_size(&cs);
+        list_append_number(rettv->vval.v_list, (varnumber_T)cs.cs_xpixel);
+        list_append_number(rettv->vval.v_list, (varnumber_T)cs.cs_ypixel);
+#else
         list_append_number(rettv->vval.v_list, (varnumber_T)gui.char_width);
         list_append_number(rettv->vval.v_list, (varnumber_T)gui.char_height);
+#endif
     }
     else
 #endif

src/os_unix.c

@@ -4442,7 +4442,16 @@ mch_report_winsize(int fd, int rows, int cols)
 
     // calcurate and set tty pixel size
     struct cellsize cs;
-    mch_calc_cell_size(&cs);
+#if defined(FEAT_GUI) && defined(FEAT_GUI_MACVIM)
+    if (gui.in_use)
+    {
+	gui_mch_calc_cell_size(&cs);
+    }
+    else
+#endif
+    {
+	mch_calc_cell_size(&cs);
+    }
 
     if (cs.cs_xpixel == -1)
     {

src/proto/gui_macvim.pro

@@ -43,6 +43,7 @@ void gui_mch_set_font(GuiFont font);
 void gui_mch_expand_font(optexpand_T *args, void *param, int (*add_match)(char_u *val));
 int gui_mch_adjust_charheight(void);
 int gui_mch_adjust_charwidth(void);
+void gui_mch_calc_cell_size(struct cellsize *cs_out);
 void gui_mch_beep(void);
 char_u *gui_mch_browse(int saving, char_u *title, char_u *dflt, char_u *ext, char_u *initdir, char_u *filter);
 char_u *gui_mch_browsedir(char_u *title, char_u *initdir);

src/terminal.c

@@ -4831,8 +4831,15 @@ parse_csi(
 #ifdef FEAT_GUI
 	if (gui.in_use)
 	{
+#ifdef FEAT_GUI_MACVIM
+	    struct cellsize cs;
+	    gui_mch_calc_cell_size(&cs);
+	    x += wp->w_wincol * cs.cs_xpixel;
+	    y += W_WINROW(wp) * cs.cs_ypixel;
+#else
 	    x += wp->w_wincol * gui.char_width;
 	    y += W_WINROW(wp) * gui.char_height;
+#endif
 	}
 	else
 #endif

src/testdir/test_functions.vim

@@ -4338,6 +4338,32 @@ func Test_getcellpixels_gui()
   endif
 endfunc
 
+" Test for getcellpixels() for MacVim
+func Test_getcellpixels_macvim()
+  CheckGui
+  CheckRunVimInTerminal
+  if has("gui_running") && has('gui_macvim')
+    " MacVim works asynchronously and getcellpixels() does not immediately
+    " work either at launch or after guifont has been changed. It's a
+    " deliberate design decision. Right now the caller has to wait for MacVim
+    " to update the state before getcellpixels() will reflect the correct
+    " value, hence the need for multiple wait's here.
+    call WaitForAssert({-> assert_notequal(0, getcellpixels()[0], 'Uninitialized getcellpixels')})
+    call assert_equal([7, 13], getcellpixels()) " Default font is Menlo:h11
+    set guifont=Menlo:h13
+    call WaitForAssert({-> assert_equal([8, 15], getcellpixels())})
+
+    " Also test hosting a terminal and have that be updated
+    let buf = RunVimInTerminal('', #{})
+    call term_sendkeys(buf, ":redi @\"\<CR>")
+    call term_sendkeys(buf, ":echo getcellpixels()\<CR>")
+    call term_sendkeys(buf, ":redi END\<CR>")
+    call term_sendkeys(buf, "P")
+    call WaitForAssert({-> assert_equal(string(getcellpixels()), term_getline(buf, 3))}, 1000)
+    call StopVimInTerminal(buf)
+  endif
+endfunc
+
 func Str2Blob(s)
   return list2blob(str2list(a:s))
 endfunc