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<p>To make this a little more concrete, I put together MR <a href="https://gitlab.freedesktop.org/wayland/weston/-/merge_requests/702" class="OWAAutoLink" id="LPlnk700889" previewremoved="true">https://gitlab.freedesktop.org/wayland/weston/-/merge_requests/702</a>.</p>
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<div id="divRplyFwdMsg" dir="ltr"><font face="Calibri, sans-serif" style="font-size:11pt" color="#000000"><b>From:</b> Hoosier, Matt<br>
<b>Sent:</b> Friday, October 1, 2021 2:32:04 PM<br>
<b>To:</b> wayland-devel@lists.freedesktop.org<br>
<b>Subject:</b> Add z-order control into kiosk-shell?</font>
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<p class="MsoNormal">I've been very happy to see kiosk-shell get introduced in the past year or so. It seems to tick nearly every box that I frequently find myself wanting when trying to do embedded deployment of pre-existing Wayland apps which expect to use
the customary desktop-centric shells:<o:p></o:p></p>
<p class="MsoNormal"><o:p> </o:p></p>
<ul style="margin-top:0in" type="disc">
<li class="MsoListParagraph" style="margin-left:0in;mso-list:l0 level1 lfo1">declarative control over which output gets which surface<o:p></o:p></li><li class="MsoListParagraph" style="margin-left:0in;mso-list:l0 level1 lfo1">force the apps full-screen by default<o:p></o:p></li><li class="MsoListParagraph" style="margin-left:0in;mso-list:l0 level1 lfo1">no new protocols needed<o:p></o:p></li></ul>
<p class="MsoNormal"><o:p> </o:p></p>
<p class="MsoNormal">So this is really nice. Much lower barrier to entry than IVI Shell, and certainly a better re-use story for off-the-rack applications.<o:p></o:p></p>
<p class="MsoNormal"><o:p> </o:p></p>
<p class="MsoNormal">But there's a niche that doesn't have any obvious answer yet: controlling the stacking order of different toplevel apps. It's fairly common to construct an embedded system using distributed rendering from separate programs. This means you
need a way to control which things go above or below each other to achieve the overall effect.<o:p></o:p></p>
<p class="MsoNormal"><o:p> </o:p></p>
<p class="MsoNormal">Would there be any interest in a contribution to enhance kiosk-shell to support configurable stacking orders? This might take the form of either relative specifications ("desktop surface XYZ always goes above desktop surface UWV") or absolute
z-order specifications ("desktop surface XYZ's surfaces go into weston_layer #17").<o:p></o:p></p>
<p class="MsoNormal"><o:p> </o:p></p>
<p class="MsoNormal">I haven't thought deeply yet about how the syntax for setting the stacking-order configuration in weston.ini would look. Maybe some kind of subscript annotation following the surface ID?<o:p></o:p></p>
<p class="MsoNormal"><o:p> </o:p></p>
<p class="MsoNormal"> [output]<o:p></o:p></p>
<p class="MsoNormal"> name=LVDS1<o:p></o:p></p>
<p class="MsoNormal"> # app1 goes in weston_layer 0. app2 goes in weston_layer 1<o:p></o:p></p>
<p class="MsoNormal"> app-ids=org.domain.app1[0],com.domain.app2[1]<o:p></o:p></p>
<p class="MsoNormal"><o:p> </o:p></p>
<p class="MsoNormal">Or maybe allow more than one "app-ids" line, keyed by a subscript?<o:p></o:p></p>
<p class="MsoNormal"><o:p> </o:p></p>
<p class="MsoNormal"> [output]<o:p></o:p></p>
<p class="MsoNormal"> name=LVDS1<o:p></o:p></p>
<p class="MsoNormal"> app-ids[layer0]=org.domain.app1,...<o:p></o:p></p>
<p class="MsoNormal"> app-ids[layer1]=org.domain.app3,...<o:p></o:p></p>
<p class="MsoNormal"><o:p> </o:p></p>
<p class="MsoNormal">-Matt<o:p></o:p></p>
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