08 February 2018

A Manifest does not guarantee Visual Styles

This is part 2 of the problems that arise when using manifest files. In the first part: Update doesn't load manifest file we saw how to force Windows to load the common controls version 6, rather than to default to version 5. A manifest could be included as a resource, but it can also be an external file in the same directory as the executable. External manifest files do overrule the embedded manifest resource. To be sure the Windows loader recognizes the manifest file – for GfaWin32.exe - the timestamp of the exe must be newer than the manifest’s last modified date.

But there is more. A correct manifest file and correct dates do not guarantee that version 6 is actually loaded. For instance the following must be taken into account

  • If there are spaces in the .exe name (e.g. the exe is called “this is executable.exe”), the manifest file (“this is executable.exe.manifest”) would not work – Common Controls were not displayed correctly; however, if the spaces are replaced with underscores in both files (“this_is_executable.exe” and “this_is_executable.exe.manifest”) they did.
  • An exe seems to respond better when a manifest is embedded as a resource than as a stand-alone file. With an embedded resource you have some sort of guarantee that the manifest is applied and that the common control dll is loaded.

How are controls painted?
The comctrl32.dll – both version 5 and 6 - is now responsible for the drawing of all controls, even the standard ones that used to come in user32.dll. This makes it easier to paint the controls in a  unified style, where the controls from version 6 are painted according the current theme selected by the user. Common control version 5 is not affected by the theming, all controls are painted in a default style coming with a particular Windows OS. So, even without version 6 controls slightly differ from one Windows version to the other.

When the controls from version comctrl32 version 6 are used controls can look different on every other user’s screen. The developer hasn’t much to say in this. Borders, 3D effect, text-color, and background color can all be changed by the user by selecting a new theme. After selecting a new theme the new style takes effect immediately and the look of the controls change accordingly. What’s left for the developer is defining which parts of the controls are to be used. For instance, a Command button can have a basFlat or basThreeD style, but how the resulting control looks like can not determined before hand. Some themes draw the flat and 3D style exactly the same.

Older Windows allow disabling Visual Styles
In older Windows versions the user (or system manager) can overrule the use of common controls version 6. Especially with Windows 7, Vista and XP the user can disable the Visual Styles completely in Control Panel, or only for the particular application in the Properties – Compatibility tab of the executable. So, even when your application depends on version 6, an older OS might allow to disable certain features.
Starting with Windows 8 this is no longer the case; the theming is applied to every GUI element and the user cannot disable the theming.

So, for older Windows versions it is possible that a compiled and manifested exe executes without applying theming. Although your program does load comctrl32.dll v6 it might look old-school style (but hey, it is what the user wants). You don’t know what is actually painted in this situation. In fact, with all these different OS versions and personalization settings you can not predict at all how your program will look like exactly.

Recommendations for using controls

  • Use the newer common control version 6, this ensures painting according the default theme of each new Windows update and makes your app look more up-to-date.
  • Use default settings for all controls, don’t change text color or background color, these parts are controlled by the theme.
  • Add a resource manifest to the compiled exe, since using a manifest file might give you trouble.

Note Despite these recommendation GfaWin32.exe comes with a manifest file so that users can delete the manifest and use old-style controls for their legacy programs. Do remember that users can add a manifest file to your compiled exe themselves and thereby change the overall look of your app. 

Form Editor - Differences in painting OCX
GfaWin32.exe comes with a manifest file (stripped to only load common controls version 6) and the controls are displayed in the themed style see the previous post. The IDE itself uses pure API functions to create controls, but the Form Editor behaves quite different. The Form Editor uses specific COM design-time interaction between the host (Form) and the OCX controls. The runtime GfaWin23.ocx provides two different code-paths for communication between the host (Form) and OCX controls: a run-time and a design-time handling. There might be a discrepancy between these modes. The only way you can tell if an OCX behaves as expected is by checking the result by running (F5) the program. Then test it as a compiled exe. (You can use Launch Exe from the Project menu.) There should be no reason why a program RUN in the IDE behaves different from a stand-alone exe. The exact same runtime code is executed.

Note - There is a little catch. There is a flag in the runtime (gfawin23.ocx) that is set when the IDE is active and theoretically it is possible that the runtime behaves somewhat different. In the huge COM-related disassembly it is hard to determine what it actually does. Only a stand-alone exe that gets all the attention from the runtime without keeping an eye on the IDE. This might explain the discrepancies people noticed.

Is Themes Enabled
When problems occur it is possible to inquire about the theming state of the executable. First of all you need to check whether the program is actually using common controls version 6. This is accomplished by testing CommCtlVersion  property of the Screen Object:

If Screen.CommCtlVersion >= 6
  MsgBox "Common controls version 6 loaded."

If the required common controls version is loaded we also need to know if the application is actually themed (on older Windows). The controls need to be painted using the current theme. For this purpose there are some additional APIs located in uxtheme.dll (which comes with Windows XP and later). Two of them seem to provide information about the current theming state of the application, in particular IsThemeActive() and IsAppThemed(). However they come with limitations.

  • IsThemeActive() returns TRUE when Visual Styles are enabled for the user. It is a user setting that can be changed in Control Panel for Win 7 and lower. On Windows 8 and above this function always returns TRUE. IsThemeActive() isn’t very useful, it is included in the IsAppThemed() API.
  • IsAppThemed() checks to see if theming (Visual Styles) are on, which is the same as IsThemeActive(). In addition it checks the existence of a manifest file and also the Compatibility tab of the executable’s Properties. If all three conditions are true IsAppThemed() returns TRUE.

IsAppThemed() returns true if the theming is applied to the application. If also Screen.CommCtlVersion >= 6 (thus manifest is loaded) the application uses theming for common controls version 6.  With the following code snippet you can test the current theming state of the common controls version 6.

Declare Function IsAppThemed Lib "UxTheme.dll" () As Boolean
Trace Screen.CommCtlVersion >= 6 && IsAppThemed() ' True/False

This concludes the posts on manifests to enable themed common controls. If you have any comments or question please use the Comments section below.

For more information see https://www.codeproject.com/Articles/620045/Custom-Controls-in-Win-API-Visual-Styles

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