Effects Library

histuid includes a comprehensive library of CSS effects that you can use in your themes. All effects are defined in a shared effects.css file that can be imported into any theme.

The effects library includes:

• Animations - Keyframe animations for pulsing, glowing, and attention effects
• Gradients - Reusable gradient classes for fades and overlays
• Indicators - Visual indicators for interactive elements
• Utility Classes - Ready-to-use animation and effect classes

Interactive Demo

Use this interactive demo to preview animations and see how they look on the notification popup. Select an animation and target element to see it in action.

Animationpulse-glowpulse-glow-subtlepulse-glow-intensepulse-glow-fastpulse-glow-slowshimmershimmer-fastsparklesparkle-intensetext-shadow-breathetext-shadow-floattext-shadow-dramatictext-heartbeattext-urgentpulse-errorpulse-warningpulse-successpulse-accentsparkle-errorsparkle-accentborder-glowborder-glow-intensering-glowinner-glowbox-sparkleshadow-breatheshadow-breathe-intenseshadow-floatshadow-float-intenseshadow-dramaticshadow-dramatic-intenseshadow-dropattention-pulseattention-flashheartbeaturgentborder-pulseborder-color-pulseborder-fadeborder-glow-errorborder-glow-warningborder-glow-successborder-glow-accent

TargetTitleBodyIconPopup ContainerImageProgress Bar

UrgencyNormalLowCritical

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Copy to your themeGTK4 CSS

.notification-popup.urgency-critical .notification-summary {
    animation: pulse-glow 2s ease-in-out infinite;
}

Live CSS EditorPreview Only

Customize the animation and preview changes live.

Using Effects in Your Theme

Importing the Library

Add this import at the top of your theme CSS file:

@import "effects.css";

Applying Animations

Apply animations using the CSS animation property:

/* Pulsing glow on critical notification titles */
.notification-popup.urgency-critical .notification-summary {
    color: @error_color;
    animation: pulse-error 2s ease-in-out infinite;
}

/* Sparkle effect on icons */
.notification-icon {
    animation: sparkle-accent 2.5s ease-in-out infinite;
}

/* Floating shadow on the popup */
.notification-popup {
    animation: shadow-float 3s ease-in-out infinite;
}

Animation Categories

Pulse & Glow Effects

Text and border glow animations with varying intensities and speeds.

Animation	Duration	Best For
pulse-glow-subtle	3s	Subtle ambient effects
pulse-glow	2s	Standard text highlighting
pulse-glow-intense	2s	High-visibility text
pulse-glow-fast	0.8s	Urgent attention
pulse-glow-slow	4s	Background ambient
border-glow	2s	Container borders
border-glow-intense	2s	Strong border emphasis
ring-glow	1.5s	Ring expansion effect

Shimmer & Sparkle Effects

Multi-point flickering effects that simulate glitter or sparkle.

Animation	Duration	Best For
shimmer	2s	Gentle light flickering
shimmer-fast	0.8s	Rapid attention flash
sparkle	2.5s	Glitter effect on text
sparkle-intense	2s	Strong glitter effect
box-sparkle	3s	Glitter on containers

Shadow Effects

Dynamic shadow animations for depth and emphasis.

Animation	Duration	Best For
shadow-breathe	3s	Ambient shadow pulsing
shadow-breathe-color	3s	Shadow pulsing with currentColor
shadow-float	2s	Floating card effect
shadow-dramatic	2s	Intense shadow emphasis
shadow-drop	2s	Drop shadow animation
inner-glow	2s	Inset glow effect

Intense Shadow Variants - Extra dramatic versions with more layers and higher opacity:

Animation	Duration	Best For
shadow-breathe-intense	3s	Very prominent stacked shadows
shadow-float-intense	2s	Dramatic lift with depth
shadow-dramatic-intense	2s	Maximum visibility with glow

Text Shadow Animations - Apply to text elements for drop shadow effects:

Animation	Duration	Best For
text-shadow-breathe	3s	Pulsing text drop shadow
text-shadow-float	2s	Text lift effect
text-shadow-dramatic	2s	Intense text shadow with glow

Attention Effects

High-visibility animations for urgent notifications.

Animation	Duration	Best For
attention-pulse	1.5s	General attention
attention-flash	2s	Quick flash effect
heartbeat	1.5s	Heartbeat-like pulses
text-heartbeat	1.5s	Text heartbeat effect
urgent	0.6s	Urgent/critical alerts
text-urgent	0.6s	Urgent text emphasis

Border Animations

Pulsing and fading border effects.

Animation	Duration	Best For
border-pulse	2s	Pulsing border width
border-color-pulse	2s	Border color pulsing
border-fade	3s	Subtle border fade

Indicator Bar Effects

Visual indicators for interactive elements and status markers.

Animation/Class	Duration	Best For
indicator-pulse	3s	Subtle opacity pulse for indicator bars
.right-hand-indicator	static	Inset shadow on right side

Usage example for default action indicators:

.notification-default-action-indicator {
    background-color: alpha(@accent_bg_color, 0.7);
    min-width: 4px;
    min-height: 24px;
    border-radius: 2px;
    animation: indicator-pulse 3s ease-in-out infinite;
}

/* Right-hand indicator with custom color */
.notification-popup.has-default-action {
    --indicator-color: alpha(@accent_bg_color, 0.35);
}

Stack Count Flash

Temporary highlight animation when notification stack count increases.

Animation	Duration	Best For
stack-count-flash	0.6s	Highlight when count changes

/* Applied automatically to stack count badge when count increases */
.stack-count-flash {
    animation: stack-count-flash 0.6s ease-out forwards;
}

Color Variants

Pre-defined animations using standard theme colors (error, warning, success, accent).

Error (Red):

• pulse-error, border-glow-error, sparkle-error

Warning (Yellow):

• pulse-warning, border-glow-warning

Success (Green):

• pulse-success, border-glow-success

Accent (Blue):

• pulse-accent, border-glow-accent, sparkle-accent

Gradient Classes

The effects library includes reusable gradient classes for common visual patterns.

Fade Gradients

These gradients indicate truncated or cropped content:

Class	Description	Use Case
.gradient-fade-bottom	Fades to background at bottom	Cropped images, long text
.gradient-fade-top	Fades to background at top	Scroll indicators
.gradient-fade-left	Fades to background on left	Horizontal scrolling
.gradient-fade-right	Fades to background on right	Horizontal scrolling
.gradient-fade-bottom-subtle	Subtle bottom fade (less aggressive)	Light overlays
.gradient-fade-top-subtle	Subtle top fade	Light overlays

Overlay Gradients

Gradients for darkening content or adding color overlays:

Class	Description	Use Case
.gradient-darken-bottom	Dark overlay from bottom	Text over images
.gradient-darken-top	Dark overlay from top	Text over images
.gradient-accent-bottom	Accent color overlay from bottom	Branding, emphasis
.gradient-error-bottom	Error color overlay from bottom	Critical notifications

Using Gradient Classes

Apply directly to overlay elements:

/* Custom image fade overlay */
.my-image-fade {
    @extend .gradient-fade-bottom;
    min-height: 24px;
    border-bottom-left-radius: 6px;
    border-bottom-right-radius: 6px;
}

Or use the gradient values directly:

.notification-image-fade {
    background-image: linear-gradient(
        to bottom,
        alpha(@window_bg_color, 0.0) 0%,
        alpha(@window_bg_color, 0.5) 40%,
        alpha(@window_bg_color, 0.85) 70%,
        @window_bg_color 100%
    );
}

Built-in Usage

The default theme uses .gradient-fade-bottom pattern for:

• Cropped notification images - Shows fade overlay when tall images are cropped to max height

GTK4 CSS Limitations

Browser vs GTK4

This demo runs in a web browser which has more CSS capabilities than GTK4. The animations shown here closely approximate GTK4 behavior, but some subtle differences may exist.

GTK4's CSS support is more limited than web browsers:

• No transform animations - rotate, scale, translate are not supported
• No pseudo-elements - ::before and ::after are limited
• No gradient position animations - Cannot animate gradient stops
• No CSS filters - blur(), hue-rotate() not available

The animation library works within these constraints using:

• text-shadow for text glow effects
• box-shadow for container/border effects
• opacity and border-color for visibility changes

Tips

1. Don't overuse animations - One or two animated elements per notification is usually enough
2. Match urgency to intensity - Use subtle animations for low urgency, intense for critical
3. Consider accessibility - Some users may prefer reduced motion
4. Test with real content - Animations look different with varying text lengths