Adding an About dialog as a property to a custom component: what changed

Revision 3 to 4. Removed lines have a minus sign; added lines have a plus sign.

Old	New		Line
1	1		## Summary
2	2
3	3		This article is for writers of Lazarus visual components (descended from TComponent or descendants)
4	4
5	5		- With the addition of a few lines of code to your component, it can display an 'About' property with an ellipsis button in the IDE Object Inspector
6	6		- When the application programmer using your component clicks the button in the Object Inspector, a customised modal 'About' dialog is displayed with your info on it.
7	7		- As well as an 'OK' button, the dialog can also display a 'License' button
8	8		- When clicked, this displays one of the standard licenses (GPL, LGPL etc) in a modal window
9	9
10	10		This is what the application programmer would see when he drops your component onto a form:
11	11
12	12		#### Object Inspector example screenshot
13	13
14	14		![](/wiki-images/e/ed/Screenshot_MyCustomComponent_ObjectInspector.png)
15	15
16	16		#### About dialog example screenshot
17	17
18	18		- Clicking the ellipse button shows this:
19	19
20	20		![](/wiki-images/1/18/Screenshot_MyCustomComponent_AboutBox.png)
21	21
22	22		#### License screen example screenshot
23	23
24	24		- Clicking the License button shows this:
25	25
26	26		![](/wiki-images/c/c1/Screenshot_MyCustomComponent_LGPL_LicenseScreen.png)
27	27
28	28		## Download example code
29	29
30	30		You can download the full source as described in this article from the lazarus CCR [here](https://sourceforge.net/p/lazarus-ccr/svn/HEAD/tree/components/)
31	31
32	32		## Adding an About property to your new or existing component
33	33
34	34		- Add the files aboutcomponentunit.pas and license.lrs to your component directory
35	35
36	36		1. Rename aboutcomponentunit.pas to about\<yourcomponentname\>unit.pas
37	37		2. In the pas file rename the Unit to match (1)
38	38		3. Open the renamed pas file and do Search/Replace to change all instances of "TAboutComponent" to TAbout\<yourcomponentname\>
39	39		4. In the line TAboutComponent = Class(TComponent), change the ancestor to your component's ancestor (if it's not TComponent)
40	40		5. Add the edited pas file to your component's package
41	41		6. In your component's class declaration, change it's ancestor to TAbout\<yourcomponentname\> (from step 3)
42	42		7. Compile, install and see the new clickable 'About' property in your component!
43	43
44	44		### Configuring the About property dialog
45	45
46	46		- In your component's Constructor Create() set some, all or none of the following properties:
47	47		- AboutBoxComponentName (string)
48	48		- AboutBoxWidth (integer)
49	49		- AboutBoxHeight (integer)
50	50		- AboutBoxDescription (string - can contain LineEndings)
51	51		- AboutBoxBackgroundColor (TColor, like clWhite)
52	52		- AboutBoxFontName (string)
53	53		- AboutBoxFontSize (integer)
54	54		- AboutBoxVersion (string)
55	55		- AboutBoxAuthorname (string)
56	56		- AboutBoxOrganisation (string)
57	57		- AboutBoxAuthorEmail (string)
58	58		- AboutBoxLicenseType (string e.g. 'GPL', ModifiedGPL' etc)
59	59		- You will have to recompile and reinstall your component to see the results.
60	60
61	61		## Example
62	62
63	63		- Using the component [[ScrollText]] (available [here](http://www.charcodelvalle.com/scrollingtext/scrollingtext_component.zip))
64	64		- I have already renamed the AboutComponentunit to AboutScrolltextunit, and changed the class name from TAboutComponent to TAboutScrollText
65	65		- TScrolltext is dereived from TGraphicControl so in the AboutScrollText unit I alter:
66	66
67		-	~~```~~
	67	+	```text
68	68		TAboutScrollText = class(TComponent)
69	69		```
70	70
71	71		to
72	72
73		-	~~```~~
	73	+	```text
74	74		TAboutScrollText = class(TGraphicControl)
75	75		```
76	76
77	77		- Then in my scrolltext unit, I change
78	78
79		-	~~```~~
	79	+	```text
80	80		TScrollingText = class(TGraphicControl)
81	81		```
82	82
83	83		to
84	84
85		-	~~```~~
	85	+	```text
86	86		TScrollingText = class(TAboutScrollText)
87	87		```
88	88
89	89		- Now the Scrolltext component has an 'About' property, but with default values.
90	90		- So in my TScrollingText constructor, I now set my own values:
91	91
92	92		``` pascal
93	93		constructor TScrollingText.Create(AOwner: TComponent);
94	94		begin
95	95		inherited Create(AOwner);
96	96		..other constructor code..
97	97		// About dialog
98	98		AboutBoxComponentName:='ScrollingText component';
99	99		AboutBoxWidth:=400;
100	100		// AboutBoxHeight (integer)
101	101		AboutBoxDescription:='Component that shows a scrolling window.' + LineEnding +
102	102		'Use Lines property to set text and Active=True' + LineEnding +
103	103		'to use the component';
104	104		AboutBoxBackgroundColor:=clWindow;
105	105		AboutBoxFontName:='Arial';
106	106		AboutBoxFontSize:=10;
107	107		AboutBoxVersion:=C_VERSION;
108	108		AboutBoxAuthorname:='Gordon Bamber';
109	109		AboutBoxOrganisation:='Public Domain';
110	110		AboutBoxAuthorEmail:='minesadorada@charcodelvalle.com';
111	111		AboutBoxLicenseType:='LGPL';
112	112		end;
113	113		```
114	114
115	115		- I then compile and install the scroller component to the IDE palette, and the 'About' property is part of the component.
116	116
117	117		## See Also
118	118
119	119		- [[Lazarus Nongraphical Visual Component Example Code]]
120	120		- [[ScrollText]]
121	121
122	122		---
123	123		From the Free Pascal wiki, page "Adding an About dialog as a property to a custom component", as it stood on 2016-07-15 after a change by Arent, 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).
124	124		Category: Component Creation
125	125		Category: Lazarus-CCR

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