Grid Layout

Overview

gpdf uses a 12-column grid system inspired by Bootstrap. Every row is divided into 12 equal columns, and you specify how many columns each content block spans.

Column Configurations

Full Width (12 columns)

page.AutoRow(func(r *template.RowBuilder) {
    r.Col(12, func(c *template.ColBuilder) {
        c.Text("Full width content", template.BgColor(pdf.RGBHex(0xE3F2FD)))
    })
})

┌─────────────────────────────────────────────────┐
│  Full width content                  Col 12     │
└─────────────────────────────────────────────────┘

Two Equal Columns (6 + 6)

page.AutoRow(func(r *template.RowBuilder) {
    r.Col(6, func(c *template.ColBuilder) {
        c.Text("Col 6 (left)", template.BgColor(pdf.RGBHex(0xE8F5E9)))
    })
    r.Col(6, func(c *template.ColBuilder) {
        c.Text("Col 6 (right)", template.BgColor(pdf.RGBHex(0xFFF3E0)))
    })
})

┌────────────────────────┬────────────────────────┐
│  Col 6 (left)          │  Col 6 (right)         │
└────────────────────────┴────────────────────────┘

Three Equal Columns (4 + 4 + 4)

page.AutoRow(func(r *template.RowBuilder) {
    r.Col(4, func(c *template.ColBuilder) {
        c.Text("Col 4", template.BgColor(pdf.RGBHex(0xFCE4EC)))
    })
    r.Col(4, func(c *template.ColBuilder) {
        c.Text("Col 4", template.BgColor(pdf.RGBHex(0xF3E5F5)))
    })
    r.Col(4, func(c *template.ColBuilder) {
        c.Text("Col 4", template.BgColor(pdf.RGBHex(0xE8EAF6)))
    })
})

┌────────────────┬────────────────┬────────────────┐
│  Col 4         │  Col 4         │  Col 4         │
└────────────────┴────────────────┴────────────────┘

Four Equal Columns (3 + 3 + 3 + 3)

page.AutoRow(func(r *template.RowBuilder) {
    r.Col(3, func(c *template.ColBuilder) {
        c.Text("Col 3", template.BgColor(pdf.RGBHex(0xE0F7FA)))
    })
    r.Col(3, func(c *template.ColBuilder) {
        c.Text("Col 3", template.BgColor(pdf.RGBHex(0xE0F2F1)))
    })
    r.Col(3, func(c *template.ColBuilder) {
        c.Text("Col 3", template.BgColor(pdf.RGBHex(0xFFF9C4)))
    })
    r.Col(3, func(c *template.ColBuilder) {
        c.Text("Col 3", template.BgColor(pdf.RGBHex(0xFFECB3)))
    })
})

┌───────────┬───────────┬───────────┬───────────┐
│  Col 3    │  Col 3    │  Col 3    │  Col 3    │
└───────────┴───────────┴───────────┴───────────┘

Sidebar + Main (3 + 9)

page.AutoRow(func(r *template.RowBuilder) {
    r.Col(3, func(c *template.ColBuilder) {
        c.Text("Sidebar (3)", template.BgColor(pdf.RGBHex(0xD7CCC8)))
    })
    r.Col(9, func(c *template.ColBuilder) {
        c.Text("Main content (9)", template.BgColor(pdf.RGBHex(0xF5F5F5)))
    })
})

┌───────────┬─────────────────────────────────────┐
│  Sidebar  │  Main content (9)                   │
│  (3)      │                                     │
└───────────┴─────────────────────────────────────┘

Article + Panel (8 + 4)

page.AutoRow(func(r *template.RowBuilder) {
    r.Col(8, func(c *template.ColBuilder) {
        c.Text("Article area (8)", template.BgColor(pdf.RGBHex(0xE1F5FE)))
    })
    r.Col(4, func(c *template.ColBuilder) {
        c.Text("Side panel (4)", template.BgColor(pdf.RGBHex(0xFBE9E7)))
    })
})

┌─────────────────────────────────┬───────────────┐
│  Article area (8)               │  Side panel   │
│                                 │  (4)          │
└─────────────────────────────────┴───────────────┘

Row Types

Auto-Height Rows

AutoRow adjusts its height to fit the content:

page.AutoRow(func(r *template.RowBuilder) {
    r.Col(12, func(c *template.ColBuilder) {
        c.Text("This row's height is determined by its content")
    })
})

Fixed-Height Rows

Row takes an explicit height value:

// 30mm tall row
page.Row(document.Mm(30), func(r *template.RowBuilder) {
    r.Col(12, func(c *template.ColBuilder) {
        c.Text("This row is 30mm tall", template.BgColor(pdf.RGBHex(0xE3F2FD)))
    })
})

// 50mm tall row with two columns
page.Row(document.Mm(50), func(r *template.RowBuilder) {
    r.Col(6, func(c *template.ColBuilder) {
        c.Text("Left: 50mm row", template.BgColor(pdf.RGBHex(0xE8F5E9)))
    })
    r.Col(6, func(c *template.ColBuilder) {
        c.Text("Right: 50mm row", template.BgColor(pdf.RGBHex(0xFFF3E0)))
    })
})

┌─────────────────────────────────────────────────┐
│  This row is 30mm tall                          │
│                                    height: 30mm │
└─────────────────────────────────────────────────┘

┌────────────────────────┬────────────────────────┐
│  Left: 50mm row        │  Right: 50mm row       │
│                        │                        │
│                        │                        │
│               height: 50mm                      │
└────────────────────────┴────────────────────────┘

Multiple Content in Columns

Each column can contain multiple elements stacked vertically:

page.AutoRow(func(r *template.RowBuilder) {
    r.Col(6, func(c *template.ColBuilder) {
        c.Text("Left column - line 1")
        c.Text("Left column - line 2")
        c.Text("Left column - line 3")
    })
    r.Col(6, func(c *template.ColBuilder) {
        c.Text("Right column - line 1")
        c.Text("Right column - line 2")
        c.Text("Right column - line 3")
    })
})

┌────────────────────────┬────────────────────────┐
│  Left column - line 1  │  Right column - line 1 │
│  Left column - line 2  │  Right column - line 2 │
│  Left column - line 3  │  Right column - line 3 │
└────────────────────────┴────────────────────────┘

Page Sizes

Constant	Size	Dimensions
`document.A4`	A4	210mm x 297mm
`document.A3`	A3	297mm x 420mm
`document.Letter`	US Letter	8.5" x 11"
`document.Legal`	US Legal	8.5" x 14"

Units

gpdf supports multiple units for dimensions:

Function	Unit	Example
`document.Pt(v)`	Points (1/72 inch)	`document.Pt(12)`
`document.Mm(v)`	Millimeters	`document.Mm(20)`
`document.Cm(v)`	Centimeters	`document.Cm(2.5)`
`document.In(v)`	Inches	`document.In(1)`
`document.Em(v)`	Relative to font size	`document.Em(2)`
`document.Pct(v)`	Percentage of parent	`document.Pct(50)`

Custom Margins

// Uniform margins
template.WithMargins(document.UniformEdges(document.Mm(20)))

// Custom margins per side
template.WithMargins(document.Edges{
    Top:    document.Mm(25),
    Right:  document.Mm(15),
    Bottom: document.Mm(25),
    Left:   document.Mm(15),
})

Next Steps

Styling — Colors, text decoration, and typography
Fonts — Custom fonts and CJK support
Headers & Footers — Page-level content