[EPUB reflow] We can move the offset by pinching the page

[mickael-menu]

We can move the offset of a page by pinching it, then dragging it in a single gesture.

@johanpoirier wrote in #166:

This is caused by those lines of code: https://github.com/readium/r2-navigator-kotlin/blob/develop/r2-navigator/src/main/java/org/readium/r2/navigator/R2WebView.kt#L735-L738

The mLastMotionX is set by the second finger down, so the xDiff is almost never greater than mTouchSlop: https://github.com/readium/r2-navigator-kotlin/blob/develop/r2-navigator/src/main/java/org/readium/r2/navigator/R2WebView.kt#L677

My question is: why are we mixing touch pointers values into mLastMotionX?

[mickael-menu]

Still happening, but not a major issue.

[mickael-menu]

I took a look while working on #143, and I think it's actually a useful feature/bug. This allows to stretch a text selection across two pages, by dragging it. So I didn't fix it, however once the selection is dismissed, the page will be snapped back into place.

[SeijiFukuoka]

Hi @mickael-menu, I'm trying to not allow user to text select across two pages, how i can disable this selection, could you help me?

[mickael-menu]

Try with the code from #143 (branch fix/issue-86) and see if it helps.

[SeijiFukuoka]

@mickael-menu
Unfortunately, using this branch fix/issue-86, the user can select across two pages, I have recorded a example using test-app with Moby Dick epub.

When i select one word at top area of page and try to select something above, this bug happens.

[mickael-menu]

We got some users that reported this bug but I was never able to reproduce it myself, so I'm not sure what's going on.

I wonder if the onTap event is being fired which causes the reader to go to the previous page. Would mind checking if VisualReaderFragment.onTap is being called when you try to interact with the selection handle?

[SeijiFukuoka]

I put some breakpoints and VisualReaderFragment.onTap is not being called when I interact with text selection.
I'm trying to identify which methods are called when I interact with text selection to top direction.

[mickael-menu]

Thanks, let me know if you need some help navigating the code.

I believe the selection dragging events might be handled here:

kotlin-toolkit/readium/navigator/src/main/java/org/readium/r2/navigator/R2WebView.kt

Line 692 in 7a885b1

if ((mLastMotionX > (width - mGutterSize)) || (mLastMotionX < mGutterSize)) {

[SeijiFukuoka]

I put some breakpoints and logs and unfortunately when I try to select more text to top direction, the method onTouchEvent are not called. This method are called only when we interact ou change pages without text selection selecting something.

Could be a configuration on some javascript lib related to text selection? And one interesting fact is the bug don't happen if we try to select a word at top section and drag the text selection to bottom direction of webview page.

screen-20220811-100842.mp4

I'm still searching how to not allow user to text select to top direction without returning to previous page, but if you have any other ideas, please tell me.

Thanks in advance.

[mickael-menu]

I'm not sure, could be an issue with a specific version of the Android System WebView too. Could you share which version you have on your device? You can find it in Settings > Apps > Android System WebView. Try updating it if it's outdated to see if it helps.

[SeijiFukuoka]

I have check webview version and it's at last version. Could you tell me if it's possible to log or put a breakpoint inside gesture.js file? I tried to put and debug with chrome inspect and tried to use Android.logbut without success.

[mickael-menu]

chrome://inspect and Android.log() should work, you probably didn't rebuild the JavaScript bundles:

# If you don't already have Yarn installed
$ brew install yarn

$ cd readium/navigator

# To do only the first time
$ make install

# To do every time you change a JavaScript file
$ make scripts

The Android.log() should appear in the Logcat panel if you filter by "Debug":

2022-08-16 18:54:32.865 10029-10189/org.readium.r2reader D/R2BasicWebView: JavaScript: Test log