Delphi XE2: Reloading a custom VCL style from file? - delphi

Question

I'm loading a custom style from file using:
TStyleManager.LoadFromFile(filename)
When the file is changed I want to load it again. But if I try that I get a EDuplicateStyleException because the style is already registered.
Is there a way to unload a style so I can load it again? The typical case for this is that you are making changes to a custom style and want to see it in action without restarting the whole application.

Answer 1

After scanning the sources I guess that is not possible in a straight forward way. Your only chance might be to implement some dirty hack.
Whatever you do, you should write a QC for this. Embarcadero could implement to reload the file if the style already exists instead of raising an exception. That would look like a natural behaviour to me.

Answer 2

Check this project vcl styles utils, one of the features exposed is the capacity of unload a vcl style. Just include the Vcl.Styles.Ext unit in your project and then use this code.
TStyleManager.RemoveStyle('Carbon');

Answer 3

Another idea:
This might work. Partial code for simplicity. In the code below, you first get a handle to the already registered Style. I guess then, you can dispose and re-assign the pointer with the one you loaded from the file. I believe the exception only show when you try to apply the style, not when you load it. Forgive me if I am wrong.
var
StyleName: String;
Style : TStyleManager.TStyleServicesHandle;
FileName : String;
begin
StyleName := 'Obsidian'; // or another style name
FileName := 'obsidian.vsf'; // or any other valid style file name
Style := TStyleManager.Style[ StyleName];
if Assigned( Style) then // style already registered
begin
TStyleManager.TrySetStyle( StyleName);
// insert other processing here
end
else // style not registered
begin
if TStyleManager.IsValidStyle( FileName) then
begin
Style := TStyleManager.LoadFromFile( FileName);
if Assigned( Style) then
begin
// insert other processing here, such as
// TStyleManager.SetStyle( Style);
end;
end;
end;
end;

Answer 4

Try this:
procedure TfrmMain.Button11Click(TObject *Sender);
var
MyStyle TCustomStyleServices;
const
usStylePath= 'c:\Users\Public\Documents\Embarcadero\Studio\19.0\Styles\vcl\MINE.vsf';
begin
if TStyleManager.IsValidStyle(usStylePath)
begin
// Get current style
MyStyle:= TStyleManager.Style["Emerald"]; // this will return a TCustomStyleServices obj
if (MyStyle <> NULL)
begin
// Set default Windows style (no style)
TStyleManager.SetStyle(TStyleManager.SystemStyle);
// Remove it
TStyleManager.UnRegisterStyle(MyStyle);
end;
// Load style from disk
TStyleManager.LoadFromFile(usStylePath);
TStyleManager.SetStyle(Emerald");
end;
end;
Note: I never complied the code. But it should work.
Anyway, you should use RRuz's library. He knows a lot about these VCL styles.

Answer 5

You could make a copy of each style in another file with different name of the style. Then you could load it's copy as a workaround. If you really need original then you can load it after loading copy.