Pros of Calibre

• Comprehensive e-book management with library organization, metadata editing, and format conversion
• Cross-platform support (Windows, macOS, Linux) with a user-friendly GUI
• Extensive plugin ecosystem for customization and additional features

Cons of Calibre

• Larger resource footprint and slower startup time
• More complex interface with a steeper learning curve
• Not optimized for minimalist, distraction-free reading experience

Code Comparison

Zathura (C):

void document_open_idle(void* data)
{
  zathura_t* zathura = data;
  if (document_info_cache_invalidate(zathura) == false) {
    return;
  }
  document_open_continue(zathura);
}

Calibre (Python):

def open_book(self, path, fmt=None, library_id=None):
    db = self.current_db.new_api
    if library_id is not None:
        db = self.get_library_data(library_id)[0]
    mi = db.add_format_with_hooks(path, fmt, run_hooks=False)
    return self.book_opened(mi.id, library_id)

Both projects handle opening documents/books, but Calibre's implementation is more complex due to its library management features and support for multiple formats.

Pros of KOReader

• Cross-platform support (Android, Linux, macOS, Windows)
• Rich feature set including dictionary lookup, text-to-speech, and cloud sync
• Highly customizable reading experience with various fonts, themes, and layouts

Cons of KOReader

• Larger codebase and potentially more complex to maintain
• May have a steeper learning curve for new users due to extensive features

Code Comparison

KOReader (Lua):

local ReaderUI = require("apps/reader/readerui")
local ReaderConfig = require("apps/reader/readerconfig")

function ReaderUI:init()
    self.config = ReaderConfig:new()
    self:setupTouchZones()
end

Zathura (C):

#include "document.h"
#include "zathura.h"

bool
document_open(zathura_t* zathura, const char* path, const char* password,
              int page_number)
{
  if (zathura == NULL || path == NULL) {
    return false;
  }
}

KOReader is written primarily in Lua, focusing on e-book functionality and cross-platform support. Zathura, written in C, is a minimalist document viewer primarily for Linux systems. KOReader offers a more feature-rich experience for e-books, while Zathura provides a lightweight, customizable viewer for various document formats.

Pros of SumatraPDF

• Cross-platform support (Windows, macOS, Linux)
• More feature-rich with annotations, bookmarks, and form filling
• Faster rendering for large PDF files

Cons of SumatraPDF

• Larger file size and resource usage
• Less customizable interface
• Not as well-integrated with Unix-like systems

Code Comparison

SumatraPDF (C++):

void WindowInfo::ShowNotification(const WCHAR* message, bool autoDismiss, bool highlight) {
    NotificationWnd* wnd = new NotificationWnd(this->hwndFrame, message, autoDismiss, highlight);
    wnd->Create();
}

Zathura (C):

void zathura_document_set_zoom(zathura_document_t* document, double zoom) {
  if (document == NULL || zoom <= 0) {
    return;
  }
  document->zoom = zoom;
}

Both projects use low-level languages for performance, but SumatraPDF's C++ code allows for more object-oriented design, while Zathura's C code is more procedural. SumatraPDF's codebase is generally more complex, reflecting its broader feature set, while Zathura's code is more minimalist and focused on core PDF viewing functionality.

Pros of pdf.js

• Cross-platform compatibility: Runs in web browsers, making it accessible on various devices and operating systems
• Rich feature set: Includes annotations, text selection, and search functionality
• Easily embeddable: Can be integrated into web applications with minimal effort

Cons of pdf.js

• Performance: May be slower than native PDF viewers, especially for large documents
• Dependency on JavaScript: Requires a JavaScript-enabled environment to function
• Limited customization: Less flexible for users who prefer a minimalist interface

Code Comparison

zathura:

void document_open_idle(void* data)
{
  zathura_t* zathura = data;
  if (document_open(zathura, zathura->document_path, zathura->password,
      ZATHURA_PAGE_NUMBER_UNSPECIFIED) == false) {
    girara_notify(zathura->ui.session, GIRARA_ERROR,
        _("Could not open document '%s'."), zathura->document_path);
  }
}

pdf.js:

PDFJS.getDocument(url).then(function(pdf) {
  pdf.getPage(1).then(function(page) {
    var scale = 1.5;
    var viewport = page.getViewport(scale);
    var canvas = document.getElementById('the-canvas');
    var context = canvas.getContext('2d');
    canvas.height = viewport.height;
    canvas.width = viewport.width;
    page.render({canvasContext: context, viewport: viewport});
  });
});