GNU LibreDWG

https://www.gnu.org/software/libredwg/manual/
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GNU LibreDWG is a free software library for reading and writing DWG files, the proprietary binary...
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### Iterating over entities inside process_BLOCK_HEADER

Source: https://www.gnu.org/software/libredwg/manual/LibreDWG.html

Example of iterating over entities from a block header using get_first_owned_entity and get_next_owned_entity.

```APIDOC
## Iterating over entities inside process_BLOCK_HEADER

### Description
Example of iterating over entities from a block header using get_first_owned_entity and get_next_owned_entity.

### Code Example
```c
Dwg_Object* obj = get_first_owned_entity(ref->obj);
while (obj)
  {
    process_object(obj);
    obj = get_next_owned_entity(ref->obj, obj);
  }
```
```

--------------------------------

### Iterating over entities using dwg_api.h functions

Source: https://www.gnu.org/software/libredwg/manual/LibreDWG.html

Example of iterating over entities in model space, blocks, and paper space using the API functions from dwg_api.h.

```APIDOC
## Iterating over entities using dwg_api.h functions

### Description
Example of iterating over entities in model space, blocks, and paper space using the API functions from dwg_api.h.

### Code Example
```c
Dwg_Object_BLOCK_CONTROL* block_control = dwg_block_control(dwg);
process_BLOCK_HEADER (dwg_model_space_ref(dwg));
for (i=0; i < block_control->num_entries; i++)
  {
    process_BLOCK_HEADER (block_control->entries[i]);
  }
process_BLOCK_HEADER (dwg_paper_space_ref(dwg));
```
```

--------------------------------

### Iterating over entities using dwg.h data structures

Source: https://www.gnu.org/software/libredwg/manual/LibreDWG.html

Example of iterating over entities using the dwg.h data structures directly.

```APIDOC
## Iterating over entities using dwg.h data structures

### Description
Example of iterating over entities using the dwg.h data structures directly.

### Code Example
```c
Dwg_Object_BLOCK_CONTROL* block_control = dwg->block_control;
// first all entities in the model space
process_BLOCK_HEADER (dwg->header_vars.BLOCK_RECORD_MSPACE);
// then all entities in the blocks
for (i=0; i < block_control->num_entries; i++)
  {
    process_BLOCK_HEADER (block_control->entries[i]);
  }
// and last all entities in the paper space
process_BLOCK_HEADER (dwg->header_vars.BLOCK_RECORD_PSPACE);
```
```

--------------------------------

### dwg_dynapi_header_utf8text

Source: https://www.gnu.org/software/libredwg/manual/LibreDWG.html

Gets a UTF-8 string field from the header (database).

```APIDOC
## dwg_dynapi_header_utf8text

### Description
Accesses the Header (or Database) fields and returns a UTF-8 string.

### Function Signature
`bool dwg_dynapi_header_utf8text(void *dwg, const char *fieldname, char *textp, int *isnewp, Dwg_DYNAPI_field *fp)`

### Parameters
- **dwg** (void*) - Required - Pointer to the DWG data.
- **fieldname** (const char*) - Required - The field name to read.
- **textp** (char*) - Required - Pointer to the resulting UTF-8 string.
- **isnewp** (int*) - Required - Set to 1 if the string is a fresh copy (for unicode strings).
- **fp** (Dwg_DYNAPI_field*) - Optional - Filled with information for this field.

### Return Value
- **bool** - True on success, false on failure.
```

--------------------------------

### dwg_dynapi_entity_value

Source: https://www.gnu.org/software/libredwg/manual/LibreDWG.html

Gets the value of a field from an entity object.

```APIDOC
## dwg_dynapi_entity_value

### Description
Gets the value of a field from an entity object. The entity is of type `dwg_ent_generic`, and the field is identified by its dxfname and fieldname.

### Function Signature
`bool dwg_dynapi_entity_value(void *entity, const char *dxfname, const char *fieldname, void *out, Dwg_DYNAPI_field *fp)`

### Parameters
- **entity** (void*) - Required - Pointer to the object specific struct (dwg_ent_generic).
- **dxfname** (const char*) - Required - The dxfname of the object.
- **fieldname** (const char*) - Required - The field or property name to read.
- **out** (void*) - Required - Pointer to the result.
- **fp** (Dwg_DYNAPI_field*) - Optional - Filled with information for this field.

### Return Value
- **bool** - True on success, false on failure.
```

--------------------------------

### dwg_setup_<OBJECT>

Source: https://www.gnu.org/software/libredwg/manual/LibreDWG.html

Initializes an object for the given OBJECT or ENTITY type, with all fields zeroed. Does not initialize size, type, address, handlestream_size, or bitsize fields.

```APIDOC
## dwg_setup_<OBJECT>

### Description
Initializes an object for the given OBJECT or ENTITY type, with all fields being zeroed. This does not initialize the obj size, type, address, handlestream_size, bitsize fields.

### Function Signature
`int dwg_setup_<OBJECT>(Dwg_Object *obj)`

### Parameters
- **obj** (Dwg_Object*) - Required - Pointer to the object to initialize.

### Return Value
- **int** - Status code (0 on success).
```

--------------------------------

### dwg_dynapi_header_value

Source: https://www.gnu.org/software/libredwg/manual/LibreDWG.html

Gets the value of a header (database) field.

```APIDOC
## dwg_dynapi_header_value

### Description
Accesses the Header (or Database) fields.

### Function Signature
`bool dwg_dynapi_header_value(void *dwg, const char *fieldname, void *out, Dwg_DYNAPI_field *fp)`

### Parameters
- **dwg** (void*) - Required - Pointer to the DWG data.
- **fieldname** (const char*) - Required - The field name to read.
- **out** (void*) - Required - Pointer to the result.
- **fp** (Dwg_DYNAPI_field*) - Optional - Filled with information for this field.

### Return Value
- **bool** - True on success, false on failure.
```

--------------------------------

### dxfwrite

Source: https://www.gnu.org/software/libredwg/manual/LibreDWG.html

Creates a DXF file from a given input file (DWG, DXF, Binary DXF, JSON), optionally specifying a target version. Experimental.

```APIDOC
## dxfwrite

### Description
Create a DXF from a given input file (`DWG`, see DXF, see Binary DXF, see JSON), optionally via `--as=rNNNN` as another version. Experimental. Supports the same options as `dwg2dxf`.
```

--------------------------------

### dwg_dynapi_subclass_utf8text

Source: https://www.gnu.org/software/libredwg/manual/LibreDWG.html

Gets a UTF-8 string field from a subclass structure.

```APIDOC
## dwg_dynapi_subclass_utf8text

### Description
Accesses a subclass, a structure within the object, and returns a UTF-8 string.

### Function Signature
`bool dwg_dynapi_subclass_utf8text(void *ptr, const char *subclass, const char *fieldname, char *textp, int *isnewp, Dwg_DYNAPI_field *fp)`

### Parameters
- **ptr** (void*) - Required - Pointer to the object.
- **subclass** (const char*) - Required - The subclass name.
- **fieldname** (const char*) - Required - The field name to read.
- **textp** (char*) - Required - Pointer to the resulting UTF-8 string.
- **isnewp** (int*) - Required - Set to 1 if the string is a fresh copy (for unicode strings).
- **fp** (Dwg_DYNAPI_field*) - Optional - Filled with information for this field.

### Return Value
- **bool** - True on success, false on failure.
```

--------------------------------

### Link against LibreDWG with -lredwg

Source: https://www.gnu.org/software/libredwg/manual/LibreDWG.html

Add the linker flag -lredwg to link against the shared library libredwg. Do not use -llibredwg as it would attempt to link against liblibredwg and fail.

```makefile
AM_LDFLAGS += -lredwg

```

--------------------------------

### dwg_dynapi_entity_utf8text

Source: https://www.gnu.org/software/libredwg/manual/LibreDWG.html

Gets a UTF-8 string field from an entity object.

```APIDOC
## dwg_dynapi_entity_utf8text

### Description
Gets a UTF-8 string field from an entity object. Converts version-specific text strings to UTF-8.

### Function Signature
`bool dwg_dynapi_entity_utf8text(void *entity, const char *dxfname, const char *fieldname, char *textp, int *isnewp, Dwg_DYNAPI_field *fp)`

### Parameters
- **entity** (void*) - Required - Pointer to the entity object.
- **dxfname** (const char*) - Required - The dxfname of the object.
- **fieldname** (const char*) - Required - The field name to read.
- **textp** (char*) - Required - Pointer to the resulting UTF-8 string.
- **isnewp** (int*) - Required - Set to 1 if the string is a fresh copy (for unicode strings).
- **fp** (Dwg_DYNAPI_field*) - Optional - Filled with information for this field.

### Return Value
- **bool** - True on success, false on failure.
```

--------------------------------

### dwgwrite

Source: https://www.gnu.org/software/libredwg/manual/LibreDWG.html

Creates a DWG file from a given input file (DXF, Binary DXF, JSON), optionally specifying a target version.

```APIDOC
## dwgwrite

### Description
Create a DWG from a given input file (see DXF, see Binary DXF, see JSON), optionally via `--as=rNNNN` as another version. For now can only create r1.2-r2000 DWG files.
```

--------------------------------

### dwg_dynapi_common_value

Source: https://www.gnu.org/software/libredwg/manual/LibreDWG.html

Gets the value of a common field from an entity object.

```APIDOC
## dwg_dynapi_common_value

### Description
Accesses the common `Dwg_Object_Object*` or `Dwg_Object_Entity*` fields.

### Function Signature
`bool dwg_dynapi_common_value(void *entity, const char *fieldname, void *out, Dwg_DYNAPI_field *fp)`

### Parameters
- **entity** (void*) - Required - Pointer to the entity object.
- **fieldname** (const char*) - Required - The field name to read.
- **out** (void*) - Required - Pointer to the result.
- **fp** (Dwg_DYNAPI_field*) - Optional - Filled with information for this field.

### Return Value
- **bool** - True on success, false on failure.
```

--------------------------------

### Include LibreDWG API header

Source: https://www.gnu.org/software/libredwg/manual/LibreDWG.html

Optionally include the API header for additional API functions.

```c
#include <dwg_api.h>

```

--------------------------------

### Include LibreDWG main header

Source: https://www.gnu.org/software/libredwg/manual/LibreDWG.html

Include the main LibreDWG header to access interface elements (types and functions).

```c
#include <dwg.h>

```

--------------------------------

### dwg_dynapi_subclass_value

Source: https://www.gnu.org/software/libredwg/manual/LibreDWG.html

Gets the value of a field from a subclass structure within an object.

```APIDOC
## dwg_dynapi_subclass_value

### Description
Accesses a subclass, a structure within the object.

### Function Signature
`bool dwg_dynapi_subclass_value(void *ptr, const char *subclass, const char *fieldname, void *out, Dwg_DYNAPI_field *fp)`

### Parameters
- **ptr** (void*) - Required - Pointer to the object.
- **subclass** (const char*) - Required - The subclass name.
- **fieldname** (const char*) - Required - The field name to read.
- **out** (void*) - Required - Pointer to the result.
- **fp** (Dwg_DYNAPI_field*) - Optional - Filled with information for this field.

### Return Value
- **bool** - True on success, false on failure.
```

--------------------------------

### dwg_dynapi_common_utf8text

Source: https://www.gnu.org/software/libredwg/manual/LibreDWG.html

Gets a UTF-8 string field from common entity fields.

```APIDOC
## dwg_dynapi_common_utf8text

### Description
Gets a UTF-8 string field from common entity fields.

### Function Signature
`bool dwg_dynapi_common_utf8text(void *entity, const char *fieldname, char *textp, int *isnewp, Dwg_DYNAPI_field *fp)`

### Parameters
- **entity** (void*) - Required - Pointer to the entity object.
- **fieldname** (const char*) - Required - The field name to read.
- **textp** (char*) - Required - Pointer to the resulting UTF-8 string.
- **isnewp** (int*) - Required - Set to 1 if the string is a fresh copy (for unicode strings).
- **fp** (Dwg_DYNAPI_field*) - Optional - Filled with information for this field.

### Return Value
- **bool** - True on success, false on failure.
```

--------------------------------

### Link Against LibreDWG

Source: https://www.gnu.org/software/libredwg/manual/LibreDWG.html

Specify the linker flag to link against the LibreDWG library.

```APIDOC
## Link Against LibreDWG

### Description
When linking, specify `-lredwg` to link against the LibreDWG shared library.

### Usage
In a Makefile.am fragment:
```makefile
AM_LDFLAGS += -lredwg
```

Note: The shared object library is named `libredwg` (with system-specific extension, e.g., `.so`). Do not use `-llibredwg` as that would attempt to link against `liblibredwg` and fail.
```

--------------------------------

### Include LibreDWG Header

Source: https://www.gnu.org/software/libredwg/manual/LibreDWG.html

To access LibreDWG interface elements, include the main header file in your C code.

```APIDOC
## Include LibreDWG Header

### Description
Include the main header file to access LibreDWG interface elements.

### Usage
```c
#include <dwg.h>
```

Optionally, you can also include the API header:
```c
#include <dwg_api.h>
```
```

--------------------------------

### dwgfilter JSON filter to list layer names

Source: https://www.gnu.org/software/libredwg/manual/LibreDWG.html

Use this shell pipeline to extract layer names from a DWG file. It filters the JSON output of dwgfilter for LAYER objects and greps for the 'name' field. The example uses 'example.dwg' as the input file.

```shell
  dwgfilter '.OBJECTS[]' example.dwg | \
    grep -A22 '"object": "LAYER"' | grep name

```

--------------------------------

### dxf2dwg

Source: https://www.gnu.org/software/libredwg/manual/LibreDWG.html

Converts DXF (or Binary DXF) files to DWG, optionally specifying a target version. Experimental.

```APIDOC
## dxf2dwg

### Description
Converts DXF (or Binary DXF) files to DWG, optionally via `--as=rVER` as another version, an earlier or later version.

### Options
- `--as=rVER` - specify target version.
- `--overwrite` or `-y` - overwrite existing files.

### Notes
The DWG files are created in the current directory and not overwritten, unless the option `--overwrite` or `-y` is given. This program is experimental and AutoCAD ® may fail to import it. For now can only create r1.2-r2000 DWG. The default is writing as r2000.
```

--------------------------------

### Iterate over entities using direct data structures

Source: https://www.gnu.org/software/libredwg/manual/LibreDWG.html

Iterates over all entities in model space, blocks, and paper space using the dwg->block_control and header_vars. Requires a custom process_BLOCK_HEADER function.

```c
  Dwg_Object_BLOCK_CONTROL* block_control = dwg->block_control;
  // first all entities in the model space
  process_BLOCK_HEADER (dwg->header_vars.BLOCK_RECORD_MSPACE);
  // then all entities in the blocks
  for (i=0; i < block_control->num_entries; i++)
    {
      process_BLOCK_HEADER (block_control->entries[i]);
    }
  // and last all entities in the paper space
  process_BLOCK_HEADER (dwg->header_vars.BLOCK_RECORD_PSPACE);
```

--------------------------------

### dwg_write_file

Source: https://www.gnu.org/software/libredwg/manual/LibreDWG.html

Opens a file and writes the DWG data to it. Returns 0 on success.

```APIDOC
## dwg_write_file

### Description
Opens the specified filename and writes the DWG data to it. Returns 0 if successful.

### Function Signature
`int dwg_write_file(char *filename, Dwg_Data *dwg)`

### Parameters
- **filename** (char*) - Required - The path to the file to write.
- **dwg** (Dwg_Data*) - Required - Pointer to the DWG data structure to encode.

### Return Value
- **int** - 0 on success, non-zero on failure.
```

--------------------------------

### dwg2dxf

Source: https://www.gnu.org/software/libredwg/manual/LibreDWG.html

Converts DWG files to DXF, optionally specifying a target version or minimal DXF output.

```APIDOC
## dwg2dxf

### Description
Converts DWG files to DXF, optionally via `--as=rNNNN` as another version, an earlier or later version, or via `-m` or `--minimal` as a minimal DXF version, skipping most headers vars, classes, tables and objects.

### Options
- `--binary` - as a binary DXF file, with full precision, under construction.
- `--overwrite` or `-y` - overwrite existing files.

### Notes
The DXF files are created in the current directory and not overwritten, unless the option `--overwrite` or `-y` is given.
```

--------------------------------

### dwg_add_Document

Source: https://www.gnu.org/software/libredwg/manual/LibreDWG.html

Creates an initial template DWG structure in memory, suitable for writing to DWG or DXF files. It creates ModelSpace, PaperSpace, most Tables, and basic Dictionaries.

```APIDOC
## dwg_add_Document

### Description
Creates an initial template DWG structure in memory, suitable to be written to a DWG or DXF file, without any additional table records or entities. Creates ModelSpace, PaperSpace and most Tables and basic Dictionaries.

### Function Signature
`Dwg_Data` **dwg_add_Document** `(const Dwg_Version_Type version, const int imperial, const int loglevel)`

### Parameters
- **version** (Dwg_Version_Type) - Required - The DWG version to use. When writing DWG, a version of R_2000 is recommended, only R_1_2 - R_2000 are supported yet. For DXF you can try all versions R_13 - R_2018.
- **imperial** (int) - Required - Indicates whether to use imperial units.
- **loglevel** (int) - Required - The log level for debugging.

### Returns
- **Dwg_Data** - The created DWG data structure.
```

--------------------------------

### Iterate over entities using API functions

Source: https://www.gnu.org/software/libredwg/manual/LibreDWG.html

Iterates over all entities in model space, blocks, and paper space using the API functions from dwg_api.h: dwg_block_control, dwg_model_space_ref, and dwg_paper_space_ref.

```c
  Dwg_Object_BLOCK_CONTROL* block_control = dwg_block_control(dwg);
  process_BLOCK_HEADER (dwg_model_space_ref(dwg));
  for (i=0; i < block_control->num_entries; i++)
    {
      process_BLOCK_HEADER (block_control->entries[i]);
    }
  process_BLOCK_HEADER (dwg_paper_space_ref(dwg));
```

--------------------------------

### dwglayers

Source: https://www.gnu.org/software/libredwg/manual/LibreDWG.html

Prints all layers in a DWG file, with options to show extended names, flags, and visible layers.

```APIDOC
## dwglayers

### Description
Prints all layers in a DWG. With `-x` or `--extnames` prints the extended displayed layer name with spaces, not the internally stored old-style name with `_` instead. Only relevant with old r13 and r14 DWGs, after that layers are always stored in the extended format. With `-f` or `--flags` also the status of frown, on/off and locked. With `--on` only the visible layers, which are on and not frozen.

### Options
- `-x`, `--extnames` - print extended displayed layer name.
- `-f`, `--flags` - show status of frown, on/off and locked.
- `--on` - only visible layers (on and not frozen).

### Example
You can get the same effect via this json filter:
```
  dwgfilter '.OBJECTS[]' example.dwg | \
    grep -A22 '"object": "LAYER"' | grep name
```
```

--------------------------------

### dwgrewrite

Source: https://www.gnu.org/software/libredwg/manual/LibreDWG.html

Reads and writes a DWG file, optionally converting to another version.

```APIDOC
## dwgrewrite

### Description
Read and write the DWG, optionally via `--as=rNNNN` as another version, an earlier or later version. The default is writing as r2000. For now can only create r1.2-r2000 DWG.
```
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