fix(feature:client): fix signature reset issue and enforce white canvas background

[biplab1]

Fixes - Jira-#478

Change Summary:

• Forced canvas background to white in all themes to ensure black ink signatures are visible and export-ready.
• Fixed reset button not clearing the canvas by using a shared DrawingState and adding a clear() method.

Before Fix (Dark Mode):

before-fix-client-signature-dark-mode.mp4

After Fix (Dark Mode):

after-fix-client-signature-dark-mode.mp4

Light Mode:

client-signature-light-mode.mp4

Signature Reset and Upload from Gallery:

upload-from-gallery-and-reset.mp4

• Run the static analysis check ./gradlew check or ci-prepush.sh to make sure you didn't break anything

• If you have multiple commits please combine them into one commit by squashing them.

[biplab1]

Thanks for the suggestion! While rememberSaveable works great for primitive types (which it handles automatically), DrawingState uses non-serializable types like Path, so it would require a custom Saver. I explored that, but given users can easily re-sign if the screen rotates, the added complexity doesn’t offer much real value. Keeping it simple for now.

Reference: UI Logic with rememberSaveable

rememberSaveable stores UI element state in a Bundle through the saved instance state mechanism.

It is able to store primitive types to the bundle automatically. If your state is held in a type that is not primitive, like a data class, you can use different storing mechanisms, such as using the Parcelize annotation, using Compose APIs like listSaver and mapSaver, or implementing a custom saver class extending Compose runtime Saver class.

[niyajali]

@biplab1 you can try this CMP library - https://github.com/niyajali/compose-signature

[biplab1]

@niyajali Thanks for the suggestion! I'll check out the CMP library and see if it fits our use case.