MDL-57287 themes: fix buttons in default dashboard page header

This fix modifies styling for pages having no navbar, such as the
dashboard, site home and default dashboard pages and fixes an overlap
problem with the buttons and context header.

theme/boost/classes/output/core_renderer.php

@@ -78,15 +78,17 @@ class core_renderer extends \core_renderer {
         $html .= html_writer::start_div('card');
         $html .= html_writer::start_div('card-block');
         $html .= html_writer::div($this->context_header_settings_menu(), 'pull-xs-right context-header-settings-menu');
+        $html .= html_writer::start_div('pull-xs-left');
         $html .= $this->context_header();
+        $html .= html_writer::end_div();
         $pageheadingbutton = $this->page_heading_button();
         if (empty($PAGE->layout_options['nonavbar'])) {
-            $html .= html_writer::start_div('clearfix', array('id' => 'page-navbar'));
+            $html .= html_writer::start_div('clearfix w-100 pull-xs-left', array('id' => 'page-navbar'));
             $html .= html_writer::tag('div', $this->navbar(), array('class' => 'breadcrumb-nav'));
-            $html .= html_writer::div($pageheadingbutton, 'breadcrumb-button');
+            $html .= html_writer::div($pageheadingbutton, 'breadcrumb-button pull-xs-right');
             $html .= html_writer::end_div();
         } else if ($pageheadingbutton) {
-            $html .= html_writer::div($pageheadingbutton, 'breadcrumb-button nonavbar');
+            $html .= html_writer::div($pageheadingbutton, 'breadcrumb-button nonavbar pull-xs-right');
         }
         $html .= html_writer::tag('div', $this->course_header(), array('id' => 'course-header'));
         $html .= html_writer::end_div();

theme/boost/scss/moodle/core.scss

@@ -9,9 +9,11 @@
 .context-header-settings-menu,
 .region-main-settings-menu {
     float: right;
-    width: 4em;
+    width: auto;
+    max-width: 4em;
     height: 2em;
     display: block;
+    margin-top: 4px;
 }
 
 .context-header-settings-menu .dropdown-toggle > .icon,
@@ -1782,12 +1784,12 @@ header {
 
     .page-header-image,
     .page-header-headings {
+        float: left;
         display: block;
         position: relative;
     }
 
     .page-header-image {
-        float: left;
         margin-right: 1em;
         margin-bottom: 1em;
     }

theme/boost/scss/moodle/modules.scss

@@ -192,14 +192,7 @@ select {
 }
 
 .breadcrumb-button {
-    float: right;
     margin-top: 4px;
-
-    @include media-breakpoint-up('md') {
-        &.nonavbar {
-            margin-top: -3rem;
-        }
-    }
 }
 
 .breadcrumb-button .singlebutton {