fix(fab-button): position is correct with custom sizes

core/src/components/fab-button/fab-button.scss

@@ -199,7 +199,7 @@
 // --------------------------------------------------
 
 :host(.fab-button-small) {
-  @include margin(($fab-size - $fab-small-size) * 0.5);
+  @include margin($fab-button-small-margin);
 
   width: #{$fab-small-size};
   height: #{$fab-small-size};

core/src/components/fab-button/fab-button.vars.scss

@@ -11,3 +11,6 @@ $fab-small-size:                         40px !default;
 
 /// @prop - Border radius of the FAB button
 $fab-border-radius:                     50% !default;
+
+/// @prop - Margin applied to the small FAB button
+$fab-button-small-margin: 8px !default;

core/src/components/fab-list/fab-list.scss

@@ -4,7 +4,7 @@
 // --------------------------------------------------
 
 :host {
-  @include margin($fab-size + $fab-list-margin, 0);
+  @include margin(calc(100% + #{$fab-list-margin}), 0);
 
   display: none;
   position: absolute;
@@ -13,8 +13,15 @@
   flex-direction: column;
   align-items: center;
 
-  min-width: $fab-size;
-  min-height: $fab-size;
+  /**
+   * The list should be centered relative to the parent
+   * FAB button. We set minimum dimensions so the
+   * FAB list can be centered relative to the small FAB button.
+   * However, the small FAB button adds start/end margin, so we need
+   * to account for that in the FAB list dimensions.
+   */
+  min-width: $fab-small-size + ($fab-button-small-margin * 2);
+  min-height: $fab-small-size + ($fab-button-small-margin * 2);
 }
 
 :host(.fab-list-active) {
@@ -59,14 +66,14 @@
 }
 
 :host(.fab-list-side-start) {
-  @include margin(0, $fab-size + $fab-list-margin);
+  @include margin(0, calc(100% + #{$fab-list-margin}));
   @include position-horizontal(null, 0);
 
   flex-direction: row-reverse;
 }
 
 :host(.fab-list-side-end) {
-  @include margin(0, $fab-size + $fab-list-margin);
+  @include margin(0, calc(100% + #{$fab-list-margin}));
   @include position(null, null, null, 0);
 
   flex-direction: row;

core/src/components/fab/fab.scss

@@ -1,11 +1,15 @@
 @import "./fab.vars";
+@import "../fab-list/fab-list.vars";
 
 // Floating Action Button Container
 // --------------------------------------------------
 
 :host {
   position: absolute;
 
+  width: fit-content;
+  height: fit-content;
+
   z-index: $z-index-fixed-content;
 }
 
@@ -14,8 +18,8 @@
 // --------------------------------------------------
 
 :host(.fab-horizontal-center) {
-  @include position(null, null, null, 50%);
-  @include margin-horizontal(-$fab-size * 0.5, null);
+  @include position(null, 0px, null, 0px);
+  @include margin(null, auto);
 }
 
 :host(.fab-horizontal-start) {
@@ -38,22 +42,93 @@
   top: $fab-content-margin;
 }
 
+/**
+ * Reset the top value since edge
+ * styles use margin-top.
+ */
 :host(.fab-vertical-top.fab-edge) {
-  top: -$fab-size * 0.5;
+  top: 0;
+}
+
+/**
+ * We need to adjust the parent FAB button up by half
+ * its height so that half of it sits on the header. As a result,
+ * we target the slotted ion-fab-button instead of targeting the host.
+ */
+:host(.fab-vertical-top.fab-edge) ::slotted(ion-fab-button) {
+  margin-top: -50%;
+}
+
+/**
+ * The small FAB button adds top and bottom margin. We need to account for
+ * that margin when we adjust the FAB button for edge styles since we
+ * are overriding the margin-top value below.
+ */
+:host(.fab-vertical-top.fab-edge) ::slotted(ion-fab-button.fab-button-small) {
+  margin-top: calc((-100% + $fab-button-small-margin * 2) / 2);
+}
+
+/**
+ * Since we are adjusting the FAB button we also need
+ * to adjust the sibling ion-fab-list otherwise there will be
+ * a gap between the parent FAB button and the associated list.
+ */
+:host(.fab-vertical-top.fab-edge) ::slotted(ion-fab-list.fab-list-side-start),
+:host(.fab-vertical-top.fab-edge) ::slotted(ion-fab-list.fab-list-side-end) {
+  @include margin(-50%, null, null, null);
 }
 
+:host(.fab-vertical-top.fab-edge) ::slotted(ion-fab-list.fab-list-side-top),
+:host(.fab-vertical-top.fab-edge) ::slotted(ion-fab-list.fab-list-side-bottom) {
+  @include margin(calc(50% + #{$fab-list-margin}) null, null, null);
+}
 
 :host(.fab-vertical-bottom) {
   bottom: $fab-content-margin;
 }
 
+/**
+ * Reset the bottom value since edge
+ * styles use margin-bottom.
+ */
 :host(.fab-vertical-bottom.fab-edge) {
-  bottom: -$fab-size * 0.5;
+  bottom: 0;
 }
 
+/**
+ * We need to adjust the parent FAB button down by half
+ * its height so that half of it sits on the footer. As a result,
+ * we target the slotted ion-fab-button instead of targeting the host.
+ */
+:host(.fab-vertical-bottom.fab-edge) ::slotted(ion-fab-button) {
+  margin-bottom: -50%;
+}
 
-:host(.fab-vertical-center) {
-  @include margin(-$fab-size * 0.5, null, null, null);
+/**
+ * The small FAB button adds top and bottom margin. We need to account for
+ * that margin when we adjust the FAB button for edge styles since we
+ * are overriding the margin-bottom value below.
+ */
+:host(.fab-vertical-bottom.fab-edge) ::slotted(ion-fab-button.fab-button-small) {
+  margin-bottom: calc((-100% + $fab-button-small-margin * 2) / 2);
+}
+
+/**
+ * Since we are adjusting the FAB button we also need
+ * to adjust the sibling ion-fab-list otherwise there will be
+ * a gap between the parent FAB button and the associated list.
+ */
+:host(.fab-vertical-bottom.fab-edge) ::slotted(ion-fab-list.fab-list-side-start),
+:host(.fab-vertical-bottom.fab-edge) ::slotted(ion-fab-list.fab-list-side-end) {
+  @include margin(null, null, -50%, null);
+}
+
+:host(.fab-vertical-bottom.fab-edge) ::slotted(ion-fab-list.fab-list-side-top),
+:host(.fab-vertical-bottom.fab-edge) ::slotted(ion-fab-list.fab-list-side-bottom) {
+  @include margin(null, null, calc(50% + #{$fab-list-margin}) null);
+}
 
-  top: 50%;
+:host(.fab-vertical-center) {
+  @include position(0px, null, 0px, null);
+  @include margin(auto, null);
 }

core/src/components/fab/test/custom-size/fab.e2e.ts

@@ -0,0 +1,17 @@
+import { expect } from '@playwright/test';
+import { configs, test, Viewports } from '@utils/test/playwright';
+
+/**
+ * This behavior does not vary across modes
+ */
+configs({ modes: ['ios'] }).forEach(({ title, config, screenshot }) => {
+  test.describe(title('fab: custom size'), () => {
+    test('should position fabs correctly with custom sizes', async ({ page }) => {
+      await page.goto(`/src/components/fab/test/custom-size`, config);
+
+      await page.setViewportSize(Viewports.tablet.landscape);
+
+      await expect(page).toHaveScreenshot(screenshot(`fab-custom-size`));
+    });
+  });
+});