C# SCROLLINFO not working on Chrome window

Question

C# SCROLLINFO not working on Chrome window

Ankur Tripathi 1

I am attempting to retrieve scroll information from the window handle, but I keep getting a value of 0. I am pursuing this approach because my goal is to capture a complete scrolling screenshot of the window. The intention is to enable automatic scrolling and image capture. While I have successfully implemented automatic window scrolling, I've encountered variations in the scrolling behaviour for different windows.

For instance, sending a mouse delta of 100 results in Chrome scrolling by around 70 pixels, whereas Visual Studio scrolls by approximately 110 pixels. Each window appears to exhibit distinct scrolling characteristics. Therefore, my current objective is to calculate the precise amount of pixel movement during scrolling using the scrollbar. However, I have encountered difficulties in achieving this functionality.

Basically, I want to scroll screenshots.. so I have 2 options 1) After scrolling automatically by code calculate how much pixel scroll moved and I will capture that part and attach it to the image 2) If I am able to scroll pre-define height so, in that case, I know I scrolled 100 pixels so capture a 100-pixel image only trying option 1 but no luck yet..

Getting "False" from GetScrollInfo and GetLastError() returns 1447 error code

Code:-

// get scrollbar info
SCROLLINFO scrollinfo = new SCROLLINFO();
scrollinfo.cbSize = (uint)Marshal.SizeOf(scrollinfo);
scrollinfo.fMask = SIF_ALL; // Get all the scroll bar information.
bool horBar = GetScrollInfo1(windowHandle, SB_HORZ, out scrollinfo);
Console.WriteLine(horBar);
bool vertBar = GetScrollInfo1(windowHandle, SB_VERT, out scrollinfo);
Console.WriteLine(vertBar);
Console.WriteLine(scrollinfo.nPage + ", " + scrollinfo.nPos);

[DllImport("user32.dll")]
public static extern bool GetScrollInfo(IntPtr hWnd, int fnBar, ref SCROLLINFO lpsi);

Viorel 122.6K Reputation points

2023-08-13T14:31:47.77+00:00

What is GetScrollInfo1?

Did you check if the window uses separate scrollbar controls? (Then the code should include the SB_CTL flag and use the corresponding handles of controls).
Jeanine Zhang-MSFT 11,356 Reputation points Microsoft External Staff

2023-08-14T02:22:59.4066667+00:00

According to your description, I wonder if you mean GetScrollInfo always return 0? If so, I suggest you could try to call GetLastError to get extended error information.

"Each window appears to exhibit distinct scrolling characteristics. " As far as I'm concerned, it depends on the page size. You could refer to the Doc: Scroll Box Position and Scrolling Range
Jeanine Zhang-MSFT 11,356 Reputation points Microsoft External Staff

2023-08-15T06:06:29.18+00:00

ERROR_NO_SCROLLBARS: The window does not have scroll bars.

Applications use the GetScrollInfo function. A window receives SBM_GETSCROLLINFO message through its WindowProc function. Applications which implement a custom scroll bar control must respond to these messages for the GetScrollInfo function to work properly.

The scrollbars in Chrome are not native scrollbars, so they do not respond to the messages or the regular windowing API。

As far as I'm concerned, you couldn't use GetScrollInfo for Chrome and Visual Studio.
Ankur Tripathi 1 Reputation point

2023-08-15T06:55:18.5666667+00:00

@Jeanine Zhang-MSFT @Viorel 1) ok so is there a way to get scroll details of not native scrollbars, like Chrome?
2) Basically, I want to capture scrolling screenshots. I intend to scroll through a browser, capture images, and then stitch them together. For instance, if I scroll 100 pixels, I aim to capture the bottom 100 pixels and merge them into the main image. If I'm unable to obtain scroll bar information, could you please suggest an alternative approach? like I am able to scroll Chrome windows by code so is there a way to scroll any window 100 pixels?
Deleted

This comment has been deleted due to a violation of our Code of Conduct. The comment was manually reported or identified through automated detection before action was taken. Please refer to our Code of Conduct for more information.
Jeanine Zhang-MSFT 11,356 Reputation points Microsoft External Staff

2023-08-25T08:26:12.46+00:00

Have you checked Castorix31 's suggestion?

2 answers

Your answer

Viorel 122.6K Reputation points

2023-08-13T14:31:47.77+00:00

What is GetScrollInfo1?

Did you check if the window uses separate scrollbar controls? (Then the code should include the SB_CTL flag and use the corresponding handles of controls).
Jeanine Zhang-MSFT 11,356 Reputation points Microsoft External Staff

2023-08-14T02:22:59.4066667+00:00

According to your description, I wonder if you mean GetScrollInfo always return 0? If so, I suggest you could try to call GetLastError to get extended error information.

"Each window appears to exhibit distinct scrolling characteristics. " As far as I'm concerned, it depends on the page size. You could refer to the Doc: Scroll Box Position and Scrolling Range
Jeanine Zhang-MSFT 11,356 Reputation points Microsoft External Staff

2023-08-15T06:06:29.18+00:00

ERROR_NO_SCROLLBARS: The window does not have scroll bars.

Applications use the GetScrollInfo function. A window receives SBM_GETSCROLLINFO message through its WindowProc function. Applications which implement a custom scroll bar control must respond to these messages for the GetScrollInfo function to work properly.

The scrollbars in Chrome are not native scrollbars, so they do not respond to the messages or the regular windowing API。

As far as I'm concerned, you couldn't use GetScrollInfo for Chrome and Visual Studio.
Ankur Tripathi 1 Reputation point

2023-08-15T06:55:18.5666667+00:00

@Jeanine Zhang-MSFT @Viorel 1) ok so is there a way to get scroll details of not native scrollbars, like Chrome?
2) Basically, I want to capture scrolling screenshots. I intend to scroll through a browser, capture images, and then stitch them together. For instance, if I scroll 100 pixels, I aim to capture the bottom 100 pixels and merge them into the main image. If I'm unable to obtain scroll bar information, could you please suggest an alternative approach? like I am able to scroll Chrome windows by code so is there a way to scroll any window 100 pixels?
Deleted

This comment has been deleted due to a violation of our Code of Conduct. The comment was manually reported or identified through automated detection before action was taken. Please refer to our Code of Conduct for more information.
Jeanine Zhang-MSFT 11,356 Reputation points Microsoft External Staff

2023-08-25T08:26:12.46+00:00

Have you checked Castorix31 's suggestion?

Answer 1

Bruce (SqlWork.com) 77,686 Volunteer Moderator

The scale of the scrollbar is typically based on the size of the offscreen content. As your code has no way to detect the offscreen size, you can not calculate the number of pixels the scroll moves. Take chrome for instance, the length of the html document will control movement of the scrollbar.

Ankur Tripathi 1 Reputation point

2023-08-14T06:45:03.2666667+00:00

hey, trying to get scroll bar info using SCROLLINFO to calculate pixel scrolled.. but not getting any scroll bar details.. tried to get all ProcessModuleCollection in the handle but still not getting any details..

Basically, I want to scroll screenshots.. so I have 2 options 1) After scrolling automatically by code calculate how much pixel scroll moved and I will capture that part and attach it to the image 2) If I am able to scroll pre-define height so, in that case, I know I scrolled 100 pixels so capture a 100-pixel image only trying option 1 but no luck yet..

Answer 2

Castorix31 90,681

my goal is to capture a complete scrolling screenshot of the window.

You can use the same method as in ShareX : if GetScrollInfo fails, it compares the last 2 images to detect end of scrolling

https://github.com/ShareX/ShareX/blob/51c471113d6f5a64acc00b542ad78a0f9783ce99/ShareX.ScreenCaptureLib/Helpers/ScrollingCaptureManager.cs

(I tested with Chrome on Windows 10 22H2)

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C# SCROLLINFO not working on Chrome window

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