Fix Button minimumWidth property

Plasma's Button has an extra property "minimumWidth" which is an extra
hint not in QQC to say "what is the size to exactly fit the contents".

(it's a bit confusing, as we can perfectly handle a button below it's
"minmimum" size)

This should be based on the size the contents want to be (the
implicitWidth), not how small the contents can go (which with is pretty
meaningless when our button can elide)

It got broken at some point recently.

BUG: 353584
Change-Id: I637898c3abf98183bbae30d8f15c4d72801a3650
REVIEW: 125698

src/declarativeimports/plasmastyle/ButtonStyle.qml

@@ -32,13 +32,14 @@ import "private" as Private
 QtQuickControlStyle.ButtonStyle {
     id: style
 
+    //this is the minimum size that can hold the entire contents
     property int minimumWidth
     property int minimumHeight
 
     label: RowLayout {
         spacing: units.smallSpacing
 
-        property real minimumWidth: Layout.minimumWidth + style.padding.left + style.padding.right
+        property real minimumWidth: implicitWidth + style.padding.left + style.padding.right
         onMinimumWidthChanged: {
             if (control.minimumWidth !== undefined) {
                 style.minimumWidth = minimumWidth;
@@ -46,7 +47,7 @@ QtQuickControlStyle.ButtonStyle {
             }
         }
 
-        property real minimumHeight: Layout.preferredHeight + style.padding.top + style.padding.bottom
+        property real minimumHeight: implicitHeight + style.padding.top + style.padding.bottom
         onMinimumHeightChanged: {
             if (control.minimumHeight !== undefined) {
                 style.minimumHeight = minimumHeight;

tests/components/button.qml

@@ -7,7 +7,7 @@ import QtQuick.Layouts 1.2
 Rectangle
 {
     width: 500
-    height: 300
+    height: 500
     color: "white"
 
     Grid {
@@ -107,6 +107,17 @@ Rectangle
             }
         }
 
+        Label {
+            text: "minimum width property. Should be two letters wide"
+        }
+
+        RowLayout {
+            PlasmaComponents.Button {
+                text: "AA"
+                implicitWidth: minimumWidth
+            }
+        }
+
     }
 }