Horizontal scrolling is not reversed

[rituraj22]

Vertical scrolling is reversed, but horizontal is not. So scrolling is confusing.

[rom1v]

Thank you for the report. I currently have no way to test horizontal scrolling.

However, the documentation says:

Movements to the left generate negative x values and to the right generate positive x values. Movements down (scroll backward) generate negative y values and up (scroll forward) generate positive y values.

This seems inconsistent to me.

Since the vertical scrolling works as expected (same behavior as on desktop environments on Linux), we should reverse the horizontal scrolling.

Could you apply this change and confirms it is ok to you, please?

--- a/app/src/convert.c
+++ b/app/src/convert.c
@@ -172,7 +172,7 @@ SDL_bool mouse_wheel_from_sdl_to_android(const SDL_MouseWheelEvent *from,
     to->scroll_event.position = position;
 
     int mul = from->direction == SDL_MOUSEWHEEL_NORMAL ? 1 : -1;
-    to->scroll_event.hscroll = mul * from->x;
+    to->scroll_event.hscroll = -mul * from->x;
     to->scroll_event.vscroll = mul * from->y;
 
     return SDL_TRUE;

[rituraj22]

@rom1v Multiplying by -1 did work correctly (horizontal scrolling became reversed).
FYI, I am testing it in webview on
Micromax Canvas A1 (AQ4501)
sprout4
Android 6.0.1

[rom1v]

Thank you 👍

[rom1v]

Fixed in master.

[rituraj22]

Well I tested it on another phone with android 7.1 (Lineage OS 14.1), and in it the older version horizontal scrolling works fine and newer one has issues, so I guess it is device specific.

[rom1v]

@rituraj22 😞

The new version seems more consistent though, since the client and Android part are expressed in the same directions.

Could you add this log and provide the scrolling values for both devices for both horizontal and vertical, please?

--- a/app/src/convert.c
+++ b/app/src/convert.c
@@ -1,4 +1,5 @@
 #include "convert.h"
+#include "log.h"
 
 #define MAP(FROM, TO) case FROM: *to = TO; return SDL_TRUE
 #define FAIL default: return SDL_FALSE
@@ -172,6 +173,7 @@ SDL_bool mouse_wheel_from_sdl_to_android(const SDL_MouseWheelEvent *from,
     to->scroll_event.position = position;
 
     int mul = from->direction == SDL_MOUSEWHEEL_NORMAL ? 1 : -1;
+    LOGI("WHEEL mul=%d; (%d, %d)\n", mul, from->x, from->y);
     // SDL behavior seems inconsistent between horizontal and vertical scrolling
     // so reverse the horizontal
     // <https://wiki.libsdl.org/SDL_MouseWheelEvent#Remarks>

[rituraj22]

Log shows (-1,0) on both devices when i scroll to right. But the motion on both devices are opposite.
On the phone with 6.0, (-1,0) scrollls to right, while on 7.1, (-1,0) scrolls to left.

[rom1v]

@rituraj22 Could you provide the logs as printed please? (I also need the mul value) 😉

[rituraj22]

INFO: WHEEL mul=1; (-1, 0)
is on all cases on scroll to right

[rom1v]

On the phone with 6.0, (-1,0) scrollls to right

This is very unexpected.

Just for confirmation, it does not print:

INFO: WHEEL mul=-1; (-1, 0)

but really prints:

INFO: WHEEL mul=1; (-1, 0)

?

EDIT: my question is stupid, of course it's the same mul value, since you use the same computer.

I don't understand why it behaves that way…

[rituraj22]

Yeah on all devices it prints

For android 6.0,

INFO: Initial texture: 480x854
INFO: WHEEL mul=1; (-1, 0)
INFO: WHEEL mul=1; (0, 1)
INFO: WHEEL mul=1; (-1, 0)
INFO: WHEEL mul=1; (-1, 0)
INFO: WHEEL mul=1; (-1, 0)
INFO: WHEEL mul=1; (-1, 0)
INFO: WHEEL mul=1; (-1, 0)
INFO: WHEEL mul=1; (-1, 0)
INFO: WHEEL mul=1; (-1, 0)
INFO: WHEEL mul=1; (-1, 0)
INFO: WHEEL mul=1; (-1, 0)

On android 7.1,

INFO: Initial texture: 1080x1920
INFO: WHEEL mul=1; (-1, 0)
INFO: WHEEL mul=1; (0, 1)
INFO: WHEEL mul=1; (-1, 0)
INFO: WHEEL mul=1; (-1, 0)
INFO: WHEEL mul=1; (-1, 0)
INFO: WHEEL mul=1; (-1, 0)
INFO: WHEEL mul=1; (-1, 0)
INFO: WHEEL mul=1; (-1, 0)
INFO: WHEEL mul=1; (-1, 0)
INFO: WHEEL mul=1; (-1, 0)
INFO: WHEEL mul=1; (-1, 0)
INFO: WHEEL mul=1; (-1, 0)
INFO: WHEEL mul=1; (-1, 0)
INFO: WHEEL mul=1; (-1, 0)
INFO: WHEEL mul=1; (-1, 0)
INFO: WHEEL mul=1; (-1, 0)
INFO: WHEEL mul=1; (-1, 0)
INFO: WHEEL mul=1; (-1, 0)
INFO: WHEEL mul=1; (-1, 0)
INFO: WHEEL mul=1; (-1, 0)

[rom1v]

I said:

On the phone with 6.0, (-1,0) scrollls to right

This is very unexpected.

In fact, since I reversed the horizontal direction, the unexpected behavior is:

while on 7.1, (-1,0) scrolls to left.

[rom1v]

@rituraj22 Please confirm that #966 (comment) does not break the behavior you want.

[rom1v]

Had been fixed (see #966).