Re: How to use uxtheme APIs in custom control? - C# Discussion Boards

6-Aug-02 0:13

Hi,

I'm wrting a custom control that will use theme library to
draw my control. But whenever I call OpenThemeData, all that
I get is a NULL theme handle. Is there any trick to do before
calling this function?

I saw one guy posting the same question a couple months ago
and sought no answer.

I also read James T. Johnson & akr0's discussion on this issue.
However, not quite understand what James mean by using P/Invoke.
What's P/Invoke? (I know it may be a dump question, but I'm a
beginner...)

Any help will be appreciated. It would be better if you can
provide a code snippet to illustrate. Thanks Smile | :)

James T. Johnson6-Aug-02 1:49

6-Aug-02 1:49

Li-kai Liu (Angus) wrote:
I'm wrting a custom control that will use theme library to
draw my control.

Unless you are doing something special the "easy" thing to do is to create a manifest file for your application and set the FlatStyle of your controls to FlatStyle.System.

If you want to go this route, Chris Sells' website[^] has a manifest file for VS.NET, you can use this same file for your application just rename it to myapp.exe.manifest.

That said, on to your other question.

Li-kai Liu (Angus) wrote:
What's P/Invoke?

P/Invoke is a method of executing functions from a C-style dll in a .NET program.

The first step is to declare the function you wish to use and the file that it is in. I'll use OpenThemeData as an example. There is a step embedded in this first step, in that you have to convert all the types used into .NET equivalent types. This is something you learn with practice and time.

[DllImport("uxtheme.dll")]
public extern static IntPtr OpenThemeData(IntPtr hwnd, string pszClassList);

Note that since the second parameter is a wide string (unicode) I could just pass the string in directly and not have to involve the MarshalAs attribute.

For more information look up the DllImport and MarshalAs attributes up in MSDN. If you have to pass structures around you'll probably also need to look at the StructLayout attribute.

HTH,

James

Li-kai Liu (Angus)6-Aug-02 19:20

6-Aug-02 19:20

Hi, James

The thing you addressed in the second part using P/Inovoke
is what I've done in my program. But it's still not working.
I've already had my unmanaged function declared as you did
in the post. And it looks to me that OpenThemeData doesn't
work as it should do. I had another uxtheme API

static public extern bool IsThemeActive();

It works very well. But just don't know why OpenThemeData
always return Null whenever I call it.

Part of the code in my control is as follow:
protected override void OnPaint(PaintEventArgs pe) {

IntPtr hTheme = OpenThemeData(this.Handle , "button");

if (hTheme != IntPtr.Zero)
{
// draw themed control
}
else
{
// draw normal control
}
}

However, OpenThemeData always return Null...

Am I doing right with this?

Thanks!

James T. Johnson6-Aug-02 19:43

6-Aug-02 19:43

I think it is a result of using OpenThemeData incorrectly; but the docs aren't that clear on how it should be used. Eek! | :eek:

I only have one suggestion and it isn't a very good one. Put the class name in all caps ("BUTTON") or try "Button"

I tried to download the MSDN sample app but I just got a 404 instead Cry | :((

James

Li-kai Liu (Angus)7-Aug-02 1:03

7-Aug-02 1:03

have tired "BUTTON" & "Button". still the same Cry | :((

sample app? Do you mean ThemeExplore??

Li-kai

James T. Johnson7-Aug-02 1:07

7-Aug-02 1:07

Li-kai Liu (Angus) wrote:
Do you mean ThemeExplore

yep; I wanted to see how it used the various functions.

James

Li-kai Liu (Angus)7-Aug-02 11:20

7-Aug-02 11:20

I put a copy at http://www.ykliu.com/ThemeExplorer.zip
if you wish to have a look.

Maybe a bit slow when downloading Smile | :)

Li-kai

James T. Johnson7-Aug-02 15:06

7-Aug-02 15:06

Thanks,

Looking at the source it passes in NULL for the handle and a valid class name, so this might be the problem you are experiencing.

James

Li-kai Liu (Angus)7-Aug-02 17:45

7-Aug-02 17:45

Thanks a lot!!
You've been always helpful Smile | :)

DataReader

Mazdak5-Aug-02 20:44

Mazdak

5-Aug-02 20:44

I want to read from a "Select" SqlCommand into a SqlDataReader, but The RowsAffected
Property of the SqlDataReader doesn't show the Proper Number (Actually always -1) (how can I know how many rows have returned.)

Mazy

"If I go crazy then will you still
Call me Superman
If I’m alive and well, will you be
There holding my hand
I’ll keep you by my side with
My superhuman might
Kryptonite"Kryptonite-3 Doors Down

Re: DataReader

SimonS5-Aug-02 22:13

SimonS

5-Aug-02 22:13

A datareader is connected and forward only, so it won't contain info like rowcount, etc ...

Try use a dataset instead or loop through the datareader to see how many "reads" you can do.
Depending on the scenario, you might be able to use ExceuteScalar instead.

Cheers,
Simon

"Sign up for a chance to be among the first to experience the wrath of the gods.", Microsoft's home page (24/06/2002)

Re: DataReader

Mazdak6-Aug-02 19:12

Mazdak

6-Aug-02 19:12

Thank you for reply. Smile | :)

SimonS wrote:
t won't contain info like rowcount

But it HAS this property!!!! Confused | :confused:

Mazy

"If I go crazy then will you still
Call me Superman
If I’m alive and well, will you be
There holding my hand
I’ll keep you by my side with
My superhuman might
Kryptonite"Kryptonite-3 Doors Down

Re: DataReader

James T. Johnson6-Aug-02 19:35

6-Aug-02 19:35

It has that property, but that data isn't available until you've gone through all of the results returned.

If you run the SELECT command through query analyzer you will see the rowcount is returned as the last item.

This is done for performance reasons, so it can begin passing the data on to the next process that needs it; whether that be a parent query or a client such as the DataReader.

Otherwise it would have to load all of the results into memory, then count the number of rows before starting to send data; or perform the query twice: once to count the rows and again to send them.

This doesn't seem like much until you have a table with a million-plus rows and your query results in half of them being returned. Eek! | :eek:

James

IDE Controls Help

BLaZiNiX5-Aug-02 14:24

BLaZiNiX

5-Aug-02 14:24

Hi all,

Is there someone who know how make these 2 things

1: make a tooltip over over the cursor when someone enter a function name like in VStudio ?

2: how make a listbox appear when someone enter a "." at the end of a variable name like in VStudio ?

Thanks a lot

BLaZeX

jparsons6-Aug-02 6:22

jparsons

6-Aug-02 6:22

BLaZiNiX wrote:
2: how make a listbox appear when someone enter a "." at the end of a variable name like in VStudio ?

You could handle events like TextChanged and according to waht was typed, pop up menus.

Jared
jparsons@jparsons.org
www.prism.gatech.edu/~gte477n

BLaZiNiX6-Aug-02 13:01

BLaZiNiX

6-Aug-02 13:01

and how exactly I can find that the string I typed is the name of a variable and after I wrote a "." pop the list at the current cursor position ?

leppie7-Aug-02 2:21

leppie

7-Aug-02 2:21

Look at :

this.GetType().FindMembers()

MYrc : A .NET IRC client with C# Plugin Capabilities. See
http://sourceforge.net/projects/myrc for more info. Big Grin | :-D