Cocoa Internals/Text Controls: what changed

Revision 1 to 2. Removed lines have a minus sign; added lines have a plus sign.

Old	New		Line
1	1		## Edit
2	2
3	3		NSTextField. The field itself is readonly. Whenever it starts to edit, it's actually TCocoaFormEditor.
4	4
5	5		### MaxLength
6	6
7	7		The maximum length is not supported natively in Cocoa. There are a few ways to do that:
8	8
9	9		- textDidChange - (currently used) once the text changed - adjust it to the max length, before sending a notification
10	10		- NSFormatter - there's an example of [stackoverflow](https://stackoverflow.com/questions/827014/how-to-limit-nstextfield-text-length-and-keep-it-always-upper-case) on how to do that. But it doesn't work in Pascal
11	11
12	12		## ComboBox
13	13
14	14		Non-readonly ComboBox is implemented via NSComboBox type. Readonly combobox is implemented via NSPopupButton
15	15
16	16		### NSComboBox features
17	17
18	18		- It doesn't like to be 29px or taller in height. The height is fixed to 26 pixels
19	19		- It doesn't like custom fonts (other than default) to be assigned to itself (see [\#33626](https://bugs.freepascal.org/view.php?id=33626))
20	20
21		-	~~<figure>~~
22		-	~~<img src="cocoa_combobox_issue.png" title="cocoa_combobox_issue.png" />~~
23		-	~~<figcaption>cocoa_combobox_issue.png</figcaption>~~
24		-	~~</figure>~~
	21	+	![](/wiki-images/1/1a/Cocoa_combobox_issue.png)
25	22
26	23		### Programmatic Drop
27	24
28	25		NSAppKit doesn't provide any means to trigger the comboBox dropdown via an API call. Thus any approach would be hacking solution anyway.
29	26
30	27		There are a few options, that can be found online.
31	28
32	29		1\) Using NSAccessibility APIs [stackoverflow](https://stackoverflow.com/questions/4499262/how-to-programmatically-open-an-nscomboboxs-list)
33	30
34	31		The solution suggests using a deprecated APIs. The solution itself is pretty old, and that's why deprecated methods are used.
35	32
36	33
37	34		It should not be applied for macOS 10.11 and later.
38	35
39	36		```objc
40	37		- (void) setExpanded: (BOOL)expanded
41	38		{
42	39		id ax = NSAccessibilityUnignoredDescendant(self);
43	40		[ax accessibilitySetValue: [NSNumber numberWithBool: expanded]
44	41		forAttribute: NSAccessibilityExpandedAttribute];
45	42		}
46	43		```
47	44
48	45		2\) The same link as the method above, but it's suggesting to call popUp: selector. The selector isn't documented (but can be seen if studying backtrace) \<source lang="objc\>
49	46
50	47		`[(NSComboBoxCell*)self.acomboBox.cell performSelector:@selector(popUp:)];`
51		-
52		-	~~</source>~~
53	48
54	49		This is a hack and undesired approach, as it might cause problems in future.
55	50
56	51		3\) Instead of using popUp:, call for moveDown: which is a documented API However, it should not be called while processing the event. Instead it should be scheduled to be called after the current event is processed. As the key pressed stucks in the event queue
57	52
58	53		```delphi
59	54		procedure TCocoaComboBox.lclPopup;
60	55		var
61	56		c : NSCell;
62	57		begin
63	58		if isDown then Exit;
64	59		c:=cell;
65	60		if not Assigned(c) then Exit;
66	61		// cannot implement it immediately, as it blocks the current event processing
67	62		c.performSelector_withObject_afterDelay(
68	63		ObjCSelector('moveDown:'), nil, 0
69	64		);
70	65		end;
71	66		```
72	67
73	68		## TMemo (NSTextView)
74	69
75	70		TMemo widgetset is implemented over NSTextView and NSScrollView
76	71
77	72		By default NSTextView is designed to be constantly word-wrapped. Disabling word-wrapping could be quite complicated from a start due to odd-default values chosen by Apple, as well as complex (yet flexible) Text Layout system.
78	73
79	74		- NSTextView is a "cocoa" control, however it's not drawing the text by it's own it's also using:
80	75		- NSTextContainer. Both NSTextContainer and NSTextView settings influence on how the text is rendered in the end.
81	76
82	77		The example shows, of creating NSTextView that automatically resizes itself horizontally. However NSTextView doesn't provide its own scrollbars, thus no scrollbars would be seen.
83	78
84	79		```delphi
85	80		procedure TForm1.FormShow(Sender: TObject);
86	81		var
87	82		txt : NSTextView;
88	83		begin
89	84		txt := NSTextView.alloc.initWithFrame(NSMakeRect(10,ClientHeight-10-50,50,50));
90	85
91	86		txt.setFont(NSFont.systemFontOfSize(NSFont.systemFontSizeForControlSize(NSRegularControlSize)));
92	87
93	88		// making the maximum size - maximum!
94	89		// 10000000 is a "constant" could be found in Apple documentation
95	90		txt.setMaxSize( NSMakeSize(10000000, 10000000));
96	91		// preventing textContainer from following the width of NSTextView
97	92		txt.textContainer.setWidthTracksTextView(false);
98	93		// making TextContainer large enough.
99	94		txt.textContainer.setContainerSize ( NSMakeSize( 10000000, 1024));
100	95		// making NSTextView to resize automatically to the text boundries (max width)
101	96		txt.setHorizontallyResizable(true);
102	97
103	98		NSView(Self.Handle).addSubView(txt);
104	99		end;
105	100		```
106	101
107	102		The next step is actually to embed NSTextView into ScrollView (as a documentView).
108	103
109	104		### Inserting into Scroll View
110	105
111	106		The process is straight-forward - allocate scroll view, use NSTextView as it's document view
112	107
113	108		```delphi
114	109		procedure TForm1.FormShow(Sender: TObject);
115	110		var
116	111		txt : NSTextView;
117	112		sc : NSScrollView;
118	113		begin
119	114		txt := NSTextView.alloc.initWithFrame(NSMakeRect(10,ClientHeight-10-50,50,50));
120	115
121	116		txt.setMaxSize( NSMakeSize(10000000, 10000000));
122	117		txt.textContainer.setWidthTracksTextView(false);
123	118		txt.textContainer.setContainerSize ( NSMakeSize( 10000000, 1024));
124	119		txt.setHorizontallyResizable(true);
125	120
126	121		// allocating scroll view and placing NSTextView inside
127	122		sc := NSScrollView.alloc.initWithFrame(NSMakeRect(10,ClientHeight-10-150,150,150));
128	123		sc.setHasVerticalScroller(true);
129	124		sc.setHasHorizontalScroller(true);
130	125		sc.setAutohidesScrollers(true);
131	126		sc.setDocumentView(txt);
132	127
133	128		NSView(Self.Handle).addSubView(sc);
134	129		end;
135	130		```
136	131
137	132		Now text-view and scrollbars would act as expected.
138	133
139	134		### Line padding oddity
140	135
141	136		By default, there's 5 pixels padding between border of NSTextView and left-side of the text.
142	137
143	138		It's possible to decrease it, however, setting it to zero is causing a very weird and unpleasant glitch.
144	139
145	140		```delphi
146	141		var
147	142		txt : NSTextView;
148	143		sc : NSScrollView;
149	144		begin
150	145		txt := NSTextView.alloc.initWithFrame(NSMakeRect(10,ClientHeight-10-50,50,50));
151	146
152	147		txt.setMaxSize( NSMakeSize(10000000, 10000000));
153	148		txt.textContainer.setWidthTracksTextView(false);
154	149		txt.textContainer.setContainerSize ( NSMakeSize( 10000000, 1024));
155	150		txt.setHorizontallyResizable(true);
156	151
157	152		// setting this value to 0 is causing the problem.
158	153		txt.textContainer.setLineFragmentPadding(0);
159	154
160	155		sc := NSScrollView.alloc.initWithFrame(NSMakeRect(10,ClientHeight-10-150,150,150));
161	156		sc.setHasVerticalScroller(true);
162	157		sc.setHasHorizontalScroller(true);
163	158		sc.setAutohidesScrollers(true);
164	159		sc.setDocumentView(txt);
165	160
166	161		NSView(Self.Handle).addSubView(sc);
167	162		end;
168	163		```
169	164
170	165		Now. Everytime a new line break is added to the end of the text the view scrolls to the top (while having cursor at the bottom).
171	166
172	167		Either by pressing Enter on keyboard having cursor at the end of the text. Or by inserting a line break at the end of the text programmatically.
173	168
174	169		The only way to avoid the problem is to have Fragment padding set to a value greater than zero.
175	170
176	171		### Forcing Lines Breaks
177	172
178	173		NSTextView is a rich-text controls, thus it can (visually) handle all variety of Line breaks
179	174
180	175		- CRLF (#13#10) - Windows
181	176		- LF (#10) - Unix
182	177		- CR (#13) - Classic Mac
183	178
184	179		For consistency and Carbon compatibility, unix style (#10) is enforced.
185	180
186	181		## TSpinEdit
187	182
188	183		Spin edit control is implemented using 2 controls NSEdit and NSStepper (up/down arrow).
189	184
190	185		- Handle returned is NSEdit class. Even though the exact bounds of NSEdit ARE NOT identical to the SpinEdit boundaries. There's an additional offset to fit NSStepper
191	186		- It's possible to implement EditorEnabled property, simply by only setting NSEdit to readonly mode and allowing NSStepper to change values
192	187
193	188		## Text Input
194	189
195	190		### Dead Keys
196	191
197	192		By default Cocoa doesn't support dead keys entries for non NSTextView controls. The sample of they dead-keys can be seen, by installing (qwerty) Spanish keyboard layout (where accents are used). An accent is placed by pressing "'" followed by vowel character (a, e, i, o).
198	193
199	194		If following code is used, you should see that two key presses followed by a single unicode character generated.
200	195
201	196		Also, if "'" is followed by non-vowel character, exactly 2 separate characters would be generated
202	197
203	198		```delphi
204	199		procedure TForm1.FormKeyDown(Sender: TObject; var Key: Word; Shift: TShiftState
205	200		);
206	201		begin
207	202		case Key of
208	203		VK_SPACE, VK_BACK, VK_DELETE:
209	204		Caption := '';
210	205		else
211	206		writeln('down: ', Integer(Key));
212	207		end;
213	208		end;
214	209
215	210		procedure TForm1.FormUTF8KeyPress(Sender: TObject; var UTF8Key: TUTF8Char);
216	211		begin
217	212		if (UTF8Key <> ' ') and (UTF8Key <> #8) then begin
218	213		Caption:=Caption+UTF8Key;
219	214		writeln(UTF8Key);
220	215		end;
221	216		end;
222	217		```
223	218
224	219		## See Also
225	220
226	221		- [[Cocoa Internals]]
227	222		- [Tracking the Size of a Text View](https://developer.apple.com/library/content/documentation/Cocoa/Conceptual/TextStorageLayer/Tasks/TrackingSize.html) - Apple's official documentation explains how text size is tracked between NSViewText and NSViewContainer
228	223		- [Putting an NSTextView Object in an NSScrollView](https://developer.apple.com/library/content/documentation/Cocoa/Conceptual/TextUILayer/Tasks/TextInScrollView.html) - Apple's official documentation on how to place NSTextView into a scrollview.
229	224		- [How to Disable Word-Wrap of NSTextview](https://stackoverflow.com/questions/3174140/how-to-disable-word-wrap-of-nstextview) - stackoverflow discussion of the problem.
230	225
231	226		---
232	227		From the Free Pascal wiki, page "Cocoa Internals/Text Controls", as it stood on 2021-10-13 after a change by Skalogryz, out of the wiki's dump of 2024-05-26. Copyright stays with the author who wrote it, according to the old wiki's [[Licensing]] page. If you have concerns about this material, [message the admin](/wiki-contact).
233	228		Category: Cocoa
234	229		Category: macOS

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